The thermal lens effects in Tm:YAP laser are analyzed by solving the Poisson equation with finite difference method. The thermal focal lengths measured are in the range of 40 ? 90 mm at the pump power of 16?34 W, consistent with the simulation results. The temperature contribution coefficient (the linear coefficient between the maximum temperature in the laser crystal and the pump power) of 1.19 K/W is also obtained. The convex lens and plano-concave mirror thermal lens compensation methods are proposed and applied to a high power pumped Tm:YAP laser.