Abstract: In order to find out temperature influence on 2m KTA OPO(KTA optical parametric oscillator) laser,the temperature effect on phase-matching angle and nonlinear coefficient was calculated,the graph of the relationship between the temperature and the tunable-angle was drawn and the walk-off angle and accept angle of the phase-matched crystal in different temperature were analyzed.It was found that the crystal was in the best condition when the temperature kept in 20℃.