Evaluations of the age structure, growth pattern, and reproductive characteristics of Triplophysa stewarti are required for collecting basic biological data on Triplophysa and providing a theoretical basis for the protection of the ecological environment and fishery resources in the endorheic lake area in southern Tibet. In this study, we analyzed the age, growth, and reproductive characteristics of 1616 Triplophysa stewarti samples collected from Lake Chugutso, Tibet, using otolith identification for age data and biological measurement data. The growth equation was obtained using a functional fit, and dissected the gonads to observed their development. The age distribution of the collected Triplophysa stewarti ranged from 1 to 6 years, with fewer fishes having greater age and showing a tendency for lower age instead. The age of the female population mainly ranged from 1 to 2 years, while that of the male population mainly ranged from 3 to 4 years. The body length of all Triplophysa stewarti samples ranged from 3.47–14.30 cm, while their body weight ranged from 0.40–28.70 g. The relationship between body length and body weight was described by the linear equation, W=0.0102L^3.0115. Its growth characteristics are in accordance with the von Bertalanffy growth equation: L_t=13.891[1?e^{?0.168(t+2.895)}](R² =0.940); W_t=28.179[1? e^{?0.168(t+2.895)}] ^3.0115 (R² =0.991). The inflection age of the growth curve occurred at 3.65 years at a body length of 9.26 cm and body weight of 8.31 g. The male to female population ratio of Triplophysa stewarti was 1 : 3.01, with highly significant differences revealed by the χ² test (P＜0.01). The Fulton fertility and Clark fertility for male fishes were 1.07 and 0.88, respectively, and 1.03 and 0.76, respectively, for female fishes. The sexual maturity of Triplophysa stewarti was identified at the age of 1. Further, the maturity coefficient was 1.57% for the male population and 2.37% for the female population. Absolute fecundity ranged from 1040 to 10176 grains/tail, with an average of 4397 grains/tail. Triplophysa stewarti exhibited slow growth and less fullness, with a low gonadal maturation coefficient in females, which may be affected by the special geographical location and ecological environment of Lake Chugutso, Tibet. The age distribution of Triplophysa stewarti followed a simple pattern due to a large proportion of young individuals, which is intrinsically linked to the predatory behavior of numerous migratory and transit birds. Both the age distribution and growth characteristics of Triplophysa stewarti indicate that the population exists in a limited state. Therefore, the management of the domestic sewage and waste of the residents of Zhegu Town should be strengthened to reduce the impact of human activities on the fish habitat. Further, water flowing into the lake must be managed, the amount of water entering the lake must be monitored, and the swampiness of the lake must be reduced. A scientific guide should also be provided to the residents, and the importance of protecting local ecosystems should be emphasized.