Abstract: VISAR and X-ray were adopted and the FeMnNi alloy specimens were subjected to the shock pressure far beyond the induced phase transition pressure. Abnormal spalling behaviors were observed in the FeMnNi alloy specimens under symmetric and same thickness impact. These abnormal spalling behaviors were analyzed by the interaction among plastic wave, phase transition wave, release fan wave and rarefaction shock wave induced by reverse phase transition. Results show that phase transition and reverse phase transition occur in FeMnNi alloy, and the rarefaction shock wave induced by reverse phase transition is a main factor to result in the abnormal spalling phenomenon.