In order to study the influence of constraint conditions on the non-shock ignition reaction process of CL-20-based polymer bonded explosive (PBX) explosives, an ignition test device with adjustable mechanical constraints was used to study the reaction evolution behavior of PBX explosives under different constraints. Based on the high-speed camera image and the recovered shell wreckage, the influence of constraint conditions on the reaction rate and reaction intensity of the charge was analyzed respectively. The pressure change in the process of charge reaction was recorded by pressure sensor, and the evolution behavior of non-shock ignition reaction of explosive was analyzed. The overpressure time history of air shock wave at different positions was measured by overpressure sensor, and the detonation test of PBX was carried out. Based on the overpressure peak at the same position of the two types of tests, the relationship between constraint conditions and charge reactivity was further analyzed. The results show that weakening the mechanical constraint strength can reduce the reaction rate and the reaction intensity of the explosive. According to the pressure growth rate, the non-shock ignition reaction process under the constraint condition is divided into two stages. As the constraint strength increases, the distinction between the two reaction stages is gradually not obvious, and the first stage quickly transitions to the second stage. The parameters determined in the calculation formula of detonation overpressure peak of CL-20-based PBX explosive are A = 0.289, B = 1.041, and C = 2.224. The constraint conditions have a significant effect on the reactivity of the explosive charge. When the shell thickness is 6mm and the strength of the constraint plate is 2 MPa and 50 MPa, the reactivity of the explosive is 0.11 and 0.14, respectively. When the shell thickness is 20 mm and the strength of the constraint plate is 2 MPa, the charge reactivity is 0.31. It can be seen that the reaction intensity of CL-20-based PBX explosive can be effectively reduced by weakening the mechanical constraint strength.