With the rapid development of infrared focal plane array detector, stirling cyrocooler as a cold source has played an important role in space application. However, it is difficult to qualify its reliability and life expectancy before space application. Existing experiment and research data show that the most critical factor to restrict stirling cryocooler’s service life is working gas contamination. Based on outgassing of stirling cryocooler internal material and its relationship with temperature, time and outgassing experimental data, the failure life model of contamination is proposed. By thousands of hours of accelerated life test, two types of prototype cryocooler have been verified for applicability of the proposed life model, and the working gas analysis of tested cryocoolers also proved the existence of contamination. Afterwards, through three group contaminations adding experiment of different level water vapor, the degradation characteristics of more than 1000 hour have proved complying with the life model above. Finally, the paper further verified the applicability of this model by the fitting of experimental data of long-term running in working condition. Consequently, the life model of stirling cryocooler caused contamination degradation is established, as well as an accelerated lifetime evaluation technique was proposed for stirling cryocooler.