To evaluate the value of serum free light chain (sFLC) κ/λ ratio (sFLCR) on the diagnosis and prognosis of patients with newly diagnosed multiple myeloma(MM), and explore the effect of sFLCR normalization on the prognosis of patients after 4 courses of induction therapy. The clinical data of 43 newly diagnosed MM patients from January 2014 to January 2019 were analyzed retrospectively. Immunoturbidimetry was used to detect the expression levels of sFLC κ and λ. According to the ratio of involved and uninvolved sFLC, using 100 as a boundary, the MM patients were divided into the high ratio group (sFLCR≥100 or ≤0.01) and the low ratio group (0.01<sFLCR<100). The clinical indicators, the curative effect after 4 courses of induction therapy, and the survival time of the two groups were compared. And according to whether the sFLCR was normal after the 4 courses of induction therapy, the MM patients were divided into normal and abnormal sFLCR groups. The survival time of the two groups were compared. Compared with the low ratio group (19 cases), the high ratio group (24 cases) had elevated levels of serum creatinine and β2- microglobulin, there were more patients in DS stage III B and ISS stage III at the initial diagnosis with statistically significant (P<0.05). After 4 courses of induction therapy, compared with the low ratio group, there were fewer patients with VGPR and above response in the high ratio group (P<0.05). The median follow-up time was 20 (7-69) months. For the median progression-free survival (PFS), the high ratio group(33 months) and the low ratio group(41 months) at the initial diagnosis was statistically different (P<0.05). For the median overall survival (OS), the high ratio group(41 months) and the low ratio group(unreached) at the initial diagnosis was also statistically diffe rent (P<0.05). After 4 courses of induction therapy, the median PFS of normal group and abnormal sFLCR group was 35 months and 33 months, and the median OS was unreached and 44 months, respectively. There was no statistically significant difference (P>0.05). Patients in the high ratio group at the initial diagnosis have worse renal function, later stage of disease, lower deep remission rate, earlier disease progression, shorter survival time, and worse clinical prognosis.