Abstract: This paper reports the relation between changes of their body weight body length and their age growing of 645 Marmota sibirica.It turned out that their body weight and body length increase by degrees along with their age growing,but the increasing speed of their body weight and body length range is different.Their body weight increases more quickly and their range is larger,but their body length increases more slowly and their range is less.It proved,according to analysis of correlation that their body weight and body length are positive correlation with their age.The coefficient of crrelation and the regression equation are like this: Yw=1377.16x0.7729,Rw=0.9970; YL=33.95x0.2529,RL=0.9947.And in the terms of the significant difference (P<0.01) of their weight aver age between two neigboring age groups,the frequency disitribution overlaps unclearly and there is the feature that their changes show no difference and so on.Referring to the standard value (Mean±Sx) of their weight of eveng age group,we delimit the range of the body weight of Marmota sibirica in each age group.