To search for the opti mum physical parameters for improving the probability of resonance-enhanced mul tiphoton ionization (REMPI),this paper simulates and analyzes the influence of parameters matching of the p ump and probe lasers on the double-color double- REMPI probability.The density matrix equation theory that describes the interac tion between light and matter is adopted.It is found that the best matching condition for improving ionization probability is:(1) bo th intensities and pulse widths of two lasers are larger and equal to each other .(2) There is no relative time delay between two lasers an d the frequencies of two lasers are resonant with the corresponding transition.As for the ionization process of 1+1+1,where one pump a nd two probe photons are absorbed,the ionization probability is more sensitive to the probe laser.This indicates that in the pra ctical application,if we can not guarantee to realize the optimal matching condition,one should try to improve the intensity,pulse width a nd frequency of the probe laser.It is also found that if the lasers are not resonant with the corresponding transition,we can adopt two laser beams with complementary frequency detuning to interact with the system at the same time.Thus we can improve the io nization probability through the two-photon resonant absorption process.