Study of thermo-Optic Effects in Thermal Lens for Nd:YLF Solid State Laser and shows the results of investigation is shown that a maximum fraction of absorbed power which converted into heat is about 24% and 23% for polarized 1047 nm , polarized 1053 nm respectively. And the maximum radial temperature is 310,318 for also, the Nd:YLF crystal have a positive and negative thermal lens which effected by changing the refractive index due to the variation of temperature. The final results show that thermal effects of polarized 1047 nm is stronger than polarized 1053 nm