In order to study the influence of explosive crystal particle size on mechanical pro perties and interfacial enhancement of polymer bonded explosives (PBX), eight HMX-based PBXs were prepared by using four kinds of HMX materials with different particle size, together with fluorine resin and neutral polymer bonding agent as main explosive, binder and interface enhancement agent, respectively. The compressive stress-strain test and Brazilian test were used to obtain the compressive and tensile mechanical properties of 8 types of PBX at room temperature (20 ℃) and high temperature (60 ℃), respectively. The storage modulus and mechanical loss factor were obtained using the three-point bending mode of Dynamic Mechanical Analysis. The cross-sections of PBX were characterized by scanning electron microscopy. The compressive strength and tensile strength of PBX-nano can reach 61.3MPa and 5.7MPa, increasing by 73.1% and 63.5% compared with PBX-L, respectively. The results showed that both the compressive and tensile mechanical strength of explosives increased with the decrease of HMX particle size, in which the nano-HMX based PBX showed the highest strength. After adding the bonding agent, the compressive mechanical strength and tensile mechanical strength for all the PBX were significantly improved. The tensile strength of PBX-nano-M at 20℃ and 60℃ was up to 10.4MPa and 5.8 MPa, which was 82.6% and 101.4% higher than that of PBX-nano, respectively. The enhancement effect was that the tensile mechanical strength and the fracture work required for interface debonding and even fracture increases greatly with the decrease of particle size.