Reflection retardance induced by multi-optical coatings in output mirror of an all-solid-state single frequency V-shaped 457 nm Nd:YVO4 blue laser is reported with the theory of reflection-induced retardance by Macleod. Combining with the frequency-doubling theory of elliptical Gaussian beam under the conditions of critical phase matching, especially in type Ⅰ LiB3O5 (LBO) crystal, we discussed the influence the multi-optical coatings in output mirror on polarizing characteristic of intracavity fundamental frequency light and frequency-doubling efficiency. Research indicates that when the induced angle in output mirror is less than 15°, the refection-induced retardance is less than 2°. Furthermore, in the approximations of the exact phase matching, compared with the ideal case, the frequency-doubling efficiency reduced by multi-optical coatings is not more than 6%.