The interference mechanism of laser directional jamming to an infrared detection system was investigated in this study, and the chief jamming mode of the above-band laser was discussed. A pulsed-laser jamming experiment was conducted using the infrared detection system based on an indium antimonide (InSb) focal plane array(FPA) detector, and the response characteristics of the InSb FPA detector with above-band pulsed-laser jamming was analyzed. The failure mode and failure threshold of the InSb FPA detector were derived. The results provide a basis for further research into directional infrared countermeasure performance against infrared imaging guided weapons.