Abstract: We take 15 M_☉ model of Weaver et al. as initial model,the collapse process of stellar core between the onset of collapse and core bounce has been calculated by using the eouation of state of us (EOSⅡ).With the simplified nuclear statistical equilibrium system mentioned above, the treatment of the thermal effects of neutronization, nuclear disintegration, nuclear combination and nuclear excitation has been attemped.The results of us are essential agreed with Van Riper's results.calculated by using the ILPR's equation of state for the same initial model.As the center density of core reaches 1014gcm-3, the maximum velocity of fall and the Ms (mass at sonic point)in model D is greater than that of the typical model of Van Riper by 2.7% and 7% respectively. In model D the neutrino trapping density is less than that of the typical model of Van Riper by 3% (at mass layer 0.15M_☉) but the lepton fraction in model D is greater than that of typical model of Van Riper by 8%(at 0.15M_☉) and by 10% (at 0.5M_☉).