As an important index to evaluate the internal properties of rock and rock mass, wave velocity is significantly affected by stress and porosity. In order to study the variation of rock wave velocity with porosity and stress, acoustic-wave combination tests of two kinds of sandstone with different pores under uniaxial loading are carried out. Test results show that: The mechanical properties of sandstone not only depend on the porosity of sandstone, but also are significantly affected by pore size. Pore closure and crack propagation are the main causes of the change of wave velocity in sandstones, and the former has a more significant effect on the change of wave velocity, while the latter mainly affects the change rate of wave velocity with stress. The wave velocity of sandstones with different pores increases synchronously with stress. At the same stress level, the wave velocity of sandstones with larger porosity decreases, and the wave velocity increment increases. In the whole loading process of sandstones, porosity has the most significant effect on the changing rate of wave velocity with stress at the first stage of pore compaction.