Some key technologies of the engineering application of the fast cooldown J2T cooler and integrated Stirling cryocooler to IR detector had been studied. Such as, achievedlowest temperature, refrigerating capacity, cooldown time , cooling load , revolution perminute of controlling temperature and input power of controlling temperature etc had been discussed. Reducing thermodynamic losses, decreasing vibration noise and contamination , increasing hermetical-ly-sealed performance and assembling perfectly had been solved. Some key problems such reliability, the life time and the stores etc had been introduced in the paper.