For the first time, we have stimulated the SHG efficiency versus the polarization ratio and the crystal length of CLBO, which is pumped by the Q-switched Nd:YAG fundamental radiation with the wavelength of 1064nrn, with the shape of plane wave or the Gaussian beam, under the circumstance of phase matching. When the pumped radiation is of plane wave, the conversion efficiency of type-I and type-II SHG could be as high as 100% and 80%;when the pumped radiation is of Guassan beam, the correspondent efficiency could be 68.3% and 80%, respectively. It is necessary that the phase matching of type-II be utilized in the SHG of CLBO.