Gravels，with different granularities and compositions，are widely developed in continental faulted basin，which is the key factor that influences the velocity change of sandy conglomerate. It is not suitable to use rock physical model based on homogeneous medium. In order to accurately calculate compressional and shear wave velocities and analyze its influence factors，an extended time-average equation was established considering variable parameters through selecting 100 core samples from 10 wells in the northern steep slope of Dongying sag for ultrasonic measurement and data analysis. The contents of gravel，sand-sized clastic particle，matrix，cement and pore fluid were obtained through rock slice identification，and then compressional and shear wave velocities，obtained through ultrasonic test of core samples in the laboratory，were put into the extended time-average equation to obtain the compressional and shear wave velocities of sandy conglomerate. Model test and actual applications indicate that the calculation accuracy of compressional and shear wave velocities of sandy conglomerate derived from the extended time-average equation is 10% higher than that from Wyllie time-average equation，and the compressional and shear wave velocities derived from the extended time-average equation are more accurate than those derived from petrophysical model based on homogeneous medium.