The simplest normal form of resonant double Hopf bifurcation was studied based on Lie operator.The coefficients of the simplest normal forms of resonant double Hopf bifurcation and the nonlinear transformations in terms of the original system coefficients were given explicitly.The nonlinear transformations were used for reducing the lower-and higher-order normal forms, and the rank of system matrix was used to determine the coefficient of normal form which could be reduced.These make the gained normal form simpler than the traditional one.A general program was compiled with Mathematica.This program can compute the simplest normal form of resonant double Hopf bifurcation and the non-resonant form up to the 7th order.