Abstract: Based on Schumacher height diameter relationship equation H=1.3+αe-b/D, this paper deals with how the parameters(a and b)vary with different stand conditions.Results show that the asymptotic parameter (a) is closely correlated with the dominant height (Hd).In the above equation: H=1.3+αe-b/D, parameter a may be taken the form as a=a1Hdb1, no other stand factor is necessary for being incorporated into.Then the universal height diameter curve is constructed H=1.3+a1Hdb1e-b/D. Further analyses show that parameters a1 and b2 are of no significant regional difference while parameter b is of significant regional difference.However, we may take the same value of parameter b in different regions for one tree species with lower but practically acceptable precision.