Abstract: In order to study the effects of loading rate of stress wave on rock breaking and energy efficiency， 5 hammers with different radius of curvature were designed by using the nonlinear model of the local deformation in the longitudinal impact surface of the members. Incident stress waves with different loading rates were achieved under different and identical incident energy， and the impact test of red sandstones was conducted. The results showed that the fractal dimension of fragmentation of sandstone specimen increases linearly with the increase of the loading rate of stress wave. The fractal dimension of fragmentation of sandstone specimen increases with the increase of incident energy under the same loading rate. The energy dissipation density increases with the increase of loading rate of incident wave. Under the same loading rate， the greater the incident energy is， the greater the energy dissipation density is. The energy efficiency decreases obviously with the increase of the incident energy under different incident energy. In practice， the best incident wave must be designed considering the factors such as rock breaking and the energy efficiency.

Key words: rock breaking, impacted by pendulum hammer, same incident energy, energy efficiency