Cook-off tests for PBX-2 explosive with different heating rates of 3,5,10,25,105 ℃·min^-1 were carried out. Temperature changing processes in sample radius and sample center were recorded by thermocouples,and the reaction degree of PBX-2 explosive was gained by blast pressure gauges. Reaction behavior for PBX-2 explosive was analyzed macroscopically under heat effect. The results of the tests initially show that the reaction degree for PBX-2 explosive is reduced with high heating rate in cook-off test. Numerical simulation was made for PBX-2 explosive by Arrhenius method. Calculated temperature is accord with experimental result.