To study the effect of explosive charge defects on fast cook-off response characteristics, fast cook-off tests were conducted on type Ⅰ cook-off bomb (with defect-free charges) and type Ⅱ cook-off bomb (with defective charges). The results showed that the response time of type Ⅱ cook-off bomb (128 s) is shorter than that of type Ⅰ cook-off bomb (132 s), and the maximum shock wave overpressure at 5 m (62.7 kPa) is higher than that of type Ⅰ cook-off bomb (12.5 kPa). This indicates that the combustion of the type Ⅱ cook-off bomb was more intense than the defect-free type Ⅰ cook-off bomb after ignition, although both of them exhibit the same response level of burning reaction. Furthermore, a coupled computational model of pool fire and cook-off specimen was established to simulate the heating of the specimen in the flame using Fluent software. It is found that the closer the defect is to the charge surface, the higher local temperature at the defect, but it does not significantly affect the response time of explosive charges.