Objective: To explore the brain white matter damage in patients with moderate to severe obstructive sleep apnea hypopnea syndrome(OSAHS) using diffusional kurtosis imaging(DKI), and to analyze its relationship with anxiety, depression and cognitive impairment in patients. Methods: This was a retrospective case-control study. Fifty confirmed cases (47 males and 3 females) of moderate to severe OSAHS diagnosed by polysomnography(PSG) from November 2017 to December 2022 were selected as OSAHS group(age range from 22 to 65 years old, with median age of 40 years old), and 32 healthy controls(27 males and 5 females) of non-OSAHS diagnosed by PSG were selected as control group(age range from 19 to 56 years old, with median age of 34 years old). DKI scanning, Beck Anxiety Inventory(BAI), Beck Depression Inventory-Ⅱ(BDI-Ⅱ), and Montreal cognitive assessment(MoCA) scores were performed in all subjects. Differences in kurtosis fractional anisotropy(KFA) of various brain regions were compared between the two groups to identify differential brain regions. Correlations were analyzed between KFA reduction and anxiety, depression, and cognitive impairment in OSAHS patients. To study the correlation between brain injury and anxiety, depressive mood, and cognitive dysfunction, statistical methods such as non-parametric tests for two independent samples, chi-square tests, and partial correlation analysis, were used to analyze the evaluation indicators of the two groups. Results: The KFA values in right external capsule, left anterior corona radiata, right anterior corona radiata, left posterior corona radiata, right posterior corona radiata, left superior corona radiata, right superior corona radiata, left superior longitudinal fasciculus, right superior longitudinal fasciculus, genu of corpus callosum, splenium of corpus callosum, body of corpus callosum, posterior cingulate gyrus of moderate to severe OSAHS group were all lower than those in the control group(t=-2.247, -3.028, -3.955, -4.871, -2.632, -2.594, -2.121, -2.167, -3.129, -2.015, -2.317, -2.313, -2.152,P<0.05). For the moderate to severe OSAHS group, the correlation between AHI and KFA values of right posterior corona radiata, right superior corona radiata, left anterior corona radiata, left posterior corona radiata, left superior corona radiata, left superior longitudinal fasciculus, genu of corpus callosum, body of corpus callosum, splenium of corpus callosum were all negative(r=-0.378, -0.307, -0.337, -0.343, -0.341, -0.613, -0.390, -0.384, -0.396, P<0.05). The correlation between LSO2 and KFA values of right anterior corona radiata, right posterior corona radiata, right superior corona radiata, right superior longitudinal fasciculus, left anterior corona radiata, left posterior corona radiata, left superior corona radiata, left superior longitudinal fasciculus, genu of corpus callosum, body of corpus callosum, splenium of corpus callosum, posterior cingulate gyrus were all positive(r=0.330, 0.338, 0.425, 0.312, 0.433, 0.358, 0.410, 0.459, 0.473, 0.659, 0.489, 0.356, P<0.05). The correlation between BAI scores and KFA values of right external capsule, right anterior corona radiata, left posterior corona radiata, left superior corona radiata, body of corpus callosum, splenium of corpus callosum were all negative(r=-0.306, -0.372, -0.296, -0.346, -0.318, -0.386, P<0.05). The correlation between BDI-Ⅱ scores and KFA values of right superior corona radiata, right superior longitudinal fasciculus, left anterior corona radiata, genu of corpus callosum, body of corpus callosum, splenium of corpus callosum were all negative(r=-0.334, -0.289, -0.309, -0.310, -0.503, -0.469, P<0.05). The correlation between MoCA scores and KFA values of right posterior corona radiata, right superior longitudinal fasciculus, left anterior corona radiata, left superior corona radiata, left superior longitudinal fasciculus, genu of corpus callosum, body of corpus callosum, splenium of corpus callosum were all positive(r=0.368, 0.431, 0.324, 0.410, 0.469, 0.384, 0.369, 0.309, P<0.05). Conclusions: With the aggravation of OSAHS, the damage to some brain regions becomes more pronounced in moderate to severe OSAHS patients. These damage brain functional areas are closely related to the anxiety, depression, and cognitive impairment of patients.