To reveal the influence laws and action mechanisms of film thickness and working conditions with/without an accelerating chamber on the laser ignition performance of thin films， photoelectric detectors， high-speed cameras， spectrometers and schlieren system were adopted to investigate the laser ignition sensitivity， ignition delay time， plasma characteristics of laser-ablated thin films， laser-induced plasma shock waves and particle motion characteristics of thin films for B/KNO₃/PF energetic powder under various film thicknesses and accelerating chamber thicknesses.The results show that the 204 nm-thick Ti/Al-1 thin film facilitates the laser ignition process， lowering the laser ignition energy fluence threshold from 3.94 J·cm^-2 （without a thin film medium） to 3.67 J·cm^-2. By contrast， the 488 nm-thick Ti/Al-2 and 874 nm-thick Ti/Al-3 thin films raise the ignition energy fluence threshold， with corresponding threshold values of 4.23 J·cm^-2 and 4.85 J·cm^-2， respectively. The laser ignition delay time increases in the order of Ti/Al-1， without thin film medium， Ti/Al-2 and Ti/Al-3， following the same trend as the laser ignition energy fluence threshold. As the film thickness rises， both the electron temperature and electron density of laser-ablated film plasma decrease. When an accelerating chamber with a thickness of 0.1 mm and inner diameter of 0.6 mm is placed between the thin film and energetic powder， no obvious variation occurs in the laser ignition sensitivity of the powder. The minimum ignition delay times of the three film systems are shortened by 0.21 ms， 1.64 ms and 2.67 ms compared with the condition without an accelerating chamber， and the optimized delay times are 1.6 ms， 1.0 ms and 1.3 ms in sequence.There exists an optimal matching relationship between thin film medium thickness and accelerating chamber thickness. The Ti/Al-2 and Ti/Al-3 thin films achieve the optimal ignition performance when matched with 0.1 mm-thick and 0.2 mm-thick accelerating chambers， respectively.