Abstract: Aim To design a new device for the cook- off test safety of explosives used in in- line system. Methods One- dimension thermal explosion model was used to simulate. Results The environment temperature of explosives, propellants and initiator used in- line system in the cook - off test of insensitive munitions was calculated. Conclusion The design of the device is suitable and the device can realize the envirorument temperature of initiator in the cook- off test of munitions . This device is suited for simulating test on small size munitions.