Abstract: The development of the fiber laser-pumped optical parametric oscillator and its application in the directional infrared countermeasures technology was described. Some basic theories of laser infrared countermeasures were discussed. Based on the self-developed fiber laser-pumped continuous-wave optical parametric oscillator, 3.41, 3.63 and 3.82 m infrared lasers in the watt-level output were achieved by way of periodic tuning. The infrared jamming experiment was carried out by using all the three wavelengths of the laser and a mid-wave infrared thermography. Through comparison of the experimental results for the 3.82 m output laser in the transmission 750 m distance, it is obtained that the gray level of the infrared thermography saturated and unsaturated zone results changes greatly when the radiation density before the HgCdTe detectors is greater than 10 W/cm2. It can achieve the purpose of covering useful signal, and can make the guidance system failure.