The shock wave pulse width is one of the essential factors influencing the shock-to-detonation transition in explosives. This study experimentally investigates the pulse width effect on the shock initiation process of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Shock initiation experiments were conducted on TATB-2 explosives on the gun platform. The pulse width was controlled by varying the thickness of shock flyers. Experimental data including shock wave velocity and particle velocity after wave were recorded using the electromagnetic particle velocity meter and tracer meter. The relationships between pulse width effect, the distance to detonation, and other parameters of TATB-2 explosives were calculated and analyzed. The results demonstrate that pulse width effect significantly affects the detonation build-up process, providing essential references for understanding the shock initiation characteristics of insensitive explosives.