Abstract: This Paper is on the basis of the data from the table of standgrowth about main timber-tree species in China，to count the tree-number of stand density about different tree pecies forest-types site-classes and different mean diatmeter．Classes；Meanwhile，to courtt the tree-number reserve coeffieient(L)after Stand natural-thinning，the coefficient(L)equals the ratio that a digger diameter class comDares with a smaller diameter class．The coefficient(L)has the following law:(1)when density of stoeking is 1.0，L will increasea Iong with the increasing of stand rilean diameter．L is not a fixed ratio；(2)when density of stocking is 1.0 and stand mean diameter equals tree spacing，the L of the same tree species and different forest-type and site-class is very close each other or equal．TeSting and verifying shows L of the tree species in our country is basicallyclose or eaual．This law will provide some mportant data for forestimprovement-cutting．Srand technical mature，and growth forecast．