The coup led wave equations for ultrashort－pulse optical parametric generation (OPG) are deduced and numerically solved. The influence of the intensity and the duration of pump pulse on the characteristics of ultrashortpulse OPG are theoretically studied. Our calculation results show that the conversion efficiency of OPG and the features of the generated pulses are greatly affected by the intensity and the duration of pump pulse.The stronger the pump intensity, the higher the conversion efficiency ofOPG, and the narrower the signal pulse duration. The narrower the pump pulse duration, the greater the parameters of GVM (group－velocitymismatch among three pulses) and IGVD(intrapulse group－velocity dispersion) , the lower the conversion efficiency of OPG and the larger the duration and asymmetry degree of signal pulse.