Temperature distribution and thermal flow direction of the laser crystal rod of anisotropic thermal conductivity was studied. Elliptical isothermal contours and thermal energy of non-radial flow were obtained. It is pointed out that the transverse thermal conductivity is isotropic on a certain direction of laser rod. A simple model was used to analyse the phenomenon of thermally induced birefringence of YAlO3 laser crystal rod. Interference pattern of cross polarization for c-axis YAlO3are two sets of hyperbolas, and for b-axis YA1O3 ellipse. The observed results can be explained satisfactorily by theory.