Dynamic compression test of cement asphalt mortar(CA mortar) with field sampling specimens was carried out using an electronic universal testing machine with strain rates ranging from 1×10-5s-1 to 1×10-2s-1.Influences of strain rate on compressive strength, elastic modulus and critical strain of CA mortar were analyzed.Results show that compressive strength of CA mortar increases with increasing strain rate.There are power relationships between compressive strength, elastic modulus and critical strain of CA mortar and strain rate, and the experiential formulas are established. Defining the damage degree of CA mortar by the reduction of the tangent modulus, influence of strain rate on damage threshold of CA mortar was analyzed. It is found that the damage degree of CA mortar under low strain rate is more serious than that under high strain rate when loading to the same strain.The damage stress threshold and damage strain threshold increase with increasing strain rate. When strain rate is high, the ratio of damage stress threshold to average stress and the ratio of damage strain threshold to average strain are insensitive to strain rate.