To investigate the characteristics of rhegmatogenous retinal detachment associated with choroidal detachment (RRDCD) in a Chinese population by using ultrasound biomicroscope (UBM). A random prospective study was used to assess 1,389 patients (1,408 eyes) with rhegmatogenous retinal detachment. Comprehensive standardized ophthalmic examinations included intraocular pressure (IOP) by Goldmann applanation tonometer and the entire ocular fundus by Goldmann three-mirror lens, B-type ultrasound, and UBM. A total of 1,389 patients with rhegmatogenous retinal detachment participated in the study, including 906 men and 483 women. Two hundred and sixty-three eyes (18.79%) had RRDCD and the age of patients ranged from 9 to 82 years (median, 50.8 ± 17.7 years). Patients with high myopia (-6.00 diopters or more) represented 31.94% and more frequently experienced low intraocular pressure and multiple retinal breaks. In 263 RRDCD eyes, the results of UBM showed that ranges of choroidal detachment (CD) were <1 quadrant in 9 (3.42%) eyes, from 1 to 2 quadrants in 37 (14.07%) eyes, from 2 to 3 quadrants in 13 (4.94%) eyes, and from 3 to 4 quadrants in 204 (77.57%) eyes. ultrasound biomicroscope also showed that the angular ranges of CD were between 3.31° and 45.65° (mean, 15.98 ± 9.29°). In addition, UBM showed the mean values of CD angle for the superior (15.42 ± 9.40°), nasal (14.08 ± 8.66°), inferior (15.03 ± 9.05°), and temporal (15.96 ± 9.22°) sides. No statistically significant differences were found among any of these comparisons (F value = 2.011, P > 0.05). Retinal detachment associated with CD occurs more frequently in older people or in patients with high myopia, who usually present with low intraocular pressure and multiple retinal breaks. UBM examination can reduce false-negative rate of RRDCD, determine CD degree quantitatively, and guide classification and treatment. UBM combined with B ultrasound testing can provide a precise diagnosis of rhegmatogenous retinal detachment degree and may have important clinical significance for preoperative diagnosis of anterior proliferative vitreoretinopathy and determining operative strategy and postoperative prognosis.