In order to study characteristics of deflagration to detonation transition(DDT) of unheated and heated explosives, the DDT test device for heated explosive was designed. And the PBX-2 explosive samples with Φ30 mm×400 mm were made. The processes of temperature changing for device shell and explosive were measured by thermocouples. The transmitting time and distance were analyzed by ionic probe. The characteristic of DDT for unheated and heated explosives were gained. The results show that DDT is more difficult to occur for PBX-2 explosive at 85 ℃ than room temperature.