Currently,the damage constitutive model based on D-P（Drucker-Prager） criterion of rock has occupied dominant position in the field of damage constitutive model of rock.its advantages have become increasingly prominent.This paper mainly analyzes the results of the experimental data based on Drucker-Prager Criterion and finds some fatal errors.Poisson’ratio is key factor in it.Poisson’ratio of rock is variable value from the experimental observation.Since the Poisson’s ratio is used in the full damage constitutive model,We propose a new conception of"quasi-poisson’ratio",derived the formula of quasiPoisson’s ratio and introduce it to the constitutive model of rock based on Drucker-Prager Criterion in order to revise it.The new modified model is a new breakthrough for numerical analysis and software application.We believe the conception of "QuasiPoisson’Ratio"will lead to many aspects of the improvements in rock mechanics and has long-term meanings.