In this paper, reverse-impact method for measuring release sound velocities was improved through special treatment of the impacted face of the window, and using time-resolved velocity interferometer system for any reflector. Our experimental technique solved the problem that bulk and longitudinal sound velocities can not be obtained simultaneously using the original method reported in the literature, due to the effect of release behaviors in the buffer. With the modified reverse-impact method, sound velocities of tin were measured with higher accuracy (measuring errors of longitudinal and bulk sound velocities being about 2% and 5%, respectively) in the range of 37—80 GPa. The experimental results are consistent with thermodynamic theoretical values.