Friction sensitivity tests were conducted on the PBX-923 and PBX-2 tablets to study their reaction characteristics under compressed friction. The reaction overpressures of the explosive were obtained by blast pressure gauges to evaluate the reaction degree. Based on the data of overpressures and the recovered samples, reaction characteristics of these two explosives were analyzed. The ignition thresholds of friction work and corresponding friction powers were calculated and the ignition mechanism under compressed friction was analyzed. Results initially show that the ignition thresholds of friction work of PBX-923 and PBX-2 using smooth steel strip were more than 515.9 J and 583.2 J, respectively. And the corresponding friction powers were more than 10115 W and 11435 W, respectively. They were much higher than the ignition thresholds of friction work and the corresponding friction powers using sandy abrasive strip, which were between 294.7-368.3 J and 7.80-9.75 kW for PBX-923, and between 147.3-191.5 J and 3.90-5.07 kW for PBX-2, respectively. It confirms that the ignition of PBX is not directly caused by overall uniformly temperature rise during friction. Instead, shear induced ignition is probably the main ignition mechanism under compressed friction using sandy abrasive strap.