Age estimation is of paramount importance for studying animal population ecology. The methods of age assessment may help us to determine different individual or population criteria including growth rate, age of sexual maturity, population birth rate, survival rate, age structure, etc. Furthermore, the age and its variation can largely determine the potential and size of the population, and thus form a high population size and cause the damages. The knowledge of population age structure and composition can give us the important reference for the animals management. Plateau Zokor (Eospalax baileyi) is a typical subterranean rodent species inhabit the Qinghai-Tibetan Plateau. They usually dwell prairies, meadows and farm fields and form dense populations, destroy crops, compete with other livestock, and cause soil erosion. Even worse, Zokors population may reach pest levels when the grasslands are overgrazed by livestock and hence they aggravate the grassland degradation. In our study, 469 Plateau Zokor (260 females, 209 males) were captured in Gannan meadow, Luqu County during May to October 2015. The body length, body weight, carcass weight, propagation characteristics of each individuals was recorded, and the difference between each age groups body weights, carcass weights were analyzed by using t-test. Results show that the average body weight of female and male Zokors was significantly different (274.1 ± 2.7 g vs. 386.0 ± 5.7 g). Using body weight as the standard, Plateau Zokor can be divided into 5 natural age groups. By inter-age group differences t-test, adjacent difference between the two groups was significant (P < 0.05) (Table 1). There was no significant high correlationship between body length and body weight (Table 2). Moreover, we compared the efficiency of age determination by body weights or carcass weights, and found out that the carcass weight is the more suitable parameter. Taking the reproductive status as a reference, we divided the female and male Zokors into 5 age groups: Ⅰ, Ⅱ, Ⅲ, Ⅳ and Ⅴ (Table 3). The age determination of Plateau Zokor has followed a growth-oriented pattern in different areas and seasons in Luqu County (Fig. 1 and Fig. 2). The formula of age estimation by carcass weight obtained from the present study can be used as a reference chart in Plateau Zokor control strategies.