Abstract: Errors in the determination of the Stem volume of felled trees based on experimental datum were calculated by the appropriate formular in the past studies. Theoreitically,This paper discusses the nature and quautity of errors in the determination of volume of felled trees by Huber's,Smalian's formulas and Huber's sectional measurement formula (When form-exponent is equal to 2 or 3 q.v.the equations (3),(4),(10),(12)). The appropriate formula is proved as follows: V≈1+r+r(r-1)/2/1+r ·G·L Given V,G and L,r₁ and r₂ can be obtained by above equation.Moreover,a new method of constructing volume table could be obtained and Kunzes' equation Y²=PX^r could be applied to practice when r_{1 or r2 is regarded as a parameter.}