The dynamic impact loading has the destructive effect to the surrounding rock mass. Rock specimen such as rock plate was found to become invalid under dynamic impact loading. This paper presents brittle damage evolution law for dynamic impact damage of brittle rock based on low velocity (10m/s~40m/s) impact test, when a source of impact loading is applied to a rock plate specimen, damage cracks are developed from the source to the boundaries. This paper is concerned with the description and explanation of this phenomenon. The test results show that the cracks propagation length and break area are not arbitrary, but are influenced by the angle of dynamic impact loading. According to the test results, the study found that the scope of impact resistance optimization angle is about 30°~45°, and the cuspidal point of impact velocity is about 30m/s~35m/s; The crack length and the break area increase with the increase of the impact loading; When the break area decreases abruptly, the crack length increases suddenly, which shows that there was an obvious incubation period of crack forming, at first some pits appearing on the verge of the rock plate and the propagation rate of crack length and break area decreasing with the impact velocity increasing.