To study the mechanism of helium neon laser promoting blood vessel rebuilds in periodontium of rabbits experimental tooth movement in rabbits, He-Ne laser with the wavelength of 632.8 nm and power of 20 mW was used to irradiate periodontium of experimental tooth movement of rabbits. The result was analysised by immunohistochemistry dyeing and image analysis. The experiment show that the vascular endothelial cell growth factor (VEGF) R-2 expression where the low level laser irradiation, regardless of comparison in the pressure zone or the tension area, appears earlier, have higher peak power and longer time than it does in side irradiating. After stopping the irradiation, the expression level of the irradiation side of the VEGFR-2 is still higher than the comparison side. It shows that the biologic effect still continue after stopping the low level laser irradiation. The result indicates that the low level laser irradiation can promote the VEGFR-2 expression effectively, thus promotes the vascularization of orthodontic dental capsule and the rebuilding of bone.