The kenetic equations of quark-gluon plasma(QGP) are non-Abelian and non-linear.It is hard to solve these equations by the traditional methods.This paper suggests that the derivative expansion method is one of the effective methods to slove the nonlinear equations.However,the kenetic equations are gauge invariance,so the derivative expansion method must not violate the aguge invariance.This paper proves that the derivative expansion method violates the gauge invariance at each expansive order,but the physical result we get by...
