Impact tests on foam concrete under different maximum strain rates were performed using split Hopkinson pressure bars(SHPB). The results show that the dynamic stress strain curves of foam concrete show obvious strain rate effects. Due to the particularity of the porous structure of the material, the whole section of the curve fluctuates greatly, especially during the failure stage. In the strain softening stage, the stress value does not decrease rapidly until the bearing capacity is completely lost, but a higher stress plateau is formed, and the higher the maximum strain rate, the longer and more significant the stress plateau. Analyzed from the failure level, foam concrete is mainly destroyed in a uniform compaction mode at low maximum strain rates, while it will collapse in layers at high maximum strain rates. Based on the macro damage variables and the Zhu Wang Tang constitutive equation, the macro test results are summarized, and an approximate equivalent constitutive equation reflecting the dynamic stress strain relationship before the peak stress of the foam concrete is established through improvement.