Gymnocypris chui, also known as the Zhus naked carp, belongs to Gymnocypris, Schizothoracinae, Cyprinidae, Cypriniformes, which was mainly distributed in the Lake Lang Tso, Ngamring County, Shigatse City, Tibet Autonomous Region. The regionality and particularity of the living geographical environment for G. chui made it very sensitive to external disturbance. Once the population resources were broken, it would be difficult to recover. The study of fish life history was of great significance to the protection and exploitation of fish resources, and reproductive biology was an important part of the study of life history. To understand reproductive biology of G. chui, total 307 specimens were collected from July 2017 to June 2018 in the Lang Tso, Ngamring County, Tibet (Fig. 1 & Table 1). The total length, body length (accurate to 0.1cm) and total weight (accurate to 0.01 g) were measured in fresh state aft-r sampling. After dissection, the weight of gonad and eviscerated body weight were weighed (accurate to 0.01 g). Gender and gonadal development were judged according to the description in references. The ovaries at mature stage (Ⅳ, Ⅴ) were taken for about 5g and fixed with 6% formalin solution, and then counted with a counter. Two hundred eggs were randomly sampled from different parts of IV ovaries. The diameter of eggs (accurate to 0.01mm) was measured by micrometer. The results showed that the shape of anal fin could be used as a preliminary tool for sex discrimination of G. chui. The female''s anal fin was oval. With a slightly pointed end and smooth edge, while the male''s anal fin had a notched edge, and the last three branch fins had horny barbs (Fig. 2). The gonadosomatic index (GSI) of females and males G. chui was relative high from March to May (Fig. 3). The mean oocyte diameter was 2.18 mm, which is unimodal distribution (Fig. 4). Fulness and GSI showed the opposite trend (Fig. 5). The range of absolute fecundity was from 862 to 8 933 eggs. The mean absolute fecundity was 2 885 ± 2 765 eggs and the mean relative fecundity was 15 eggs /g (Table 2). Absolute fecundity positively correlate with body length and body weight, while relative fecundity had no significant correlation with body length and body weight (Fig. 6 & Fig. 7). The minimum size and weight were 217 mm and 122.68 g for mature females, and 198 mm and 91.93 g for mature males. The GSI were 3.92% for females and 3.34% for males. The minimum age at maturity was 7 for females and 6 for males. Sex ratio (♀︰♂) was 1︰0.967, which is consistent with the 1︰1 ratio (Table 3). During the investigation period, the water temperature of the rivers entering the lake ranged from 2.2 to 15.9 ℃ during the non-stop flow period and the freezing period, and the flow velocity ranged from 0.1 to 0.6 m/s (Table 4). These results suggest that G. chui had more yolk substances which can provide more nutrients for larvae to hatch. These results also reflect that G. chui experience more the environmental pressure in the Lang Tso.