In order to constrain the crustal wave velocity structure in the southern Tibetan crust and provide insight into the contribution of crustal composition, geothermal gradient and partial melting to the velocity structure, which is characterized by low average crustal velocities and widespread presence of low-velocity zone(s), the authors model the crustal velocity and density as functions of depth corresponding to various heat flow values in light of velocity measurements at high temperature and high pressure. The modeled velocity and density are regarded as comparison standards. The comparison of the standards with seismic observations in southern Tibet implies that the predominantly felsic composition at high heat flow cannot explain the observed velocity structure there. Hence, the authors are in favor of attributing low average crustal velocities and low-velocity zone(s) observed in southern Tibet mainly to partial melting. Modeling based on the experimental results suggests that a melting percentage of 7-12 could account for the low-velocity zone(s).