A new polymer bonded plastic explosive was developed to meet the needs of explosion hardening.The polymer bonded plastic explosive based on RDX was made up of insensitive additives,plastic additives and the additives adjusting detonation velocity.The explosion hardening experiments on Hadfield steel of rail frogs show that the hardness on the surface of rail frogs can reach from HB170-190 to HB260-280 after explosion hardening one time and to HB310-330 after explosion hardening two times.The results show that performance and hardening process of the explosive are stable and reliable.