A CW laser consisting of a low-doped Nd∶YVO4/YVO4 composite crystal and an I-type phase-matching LBO frequency-doubler with a three-mirror V-fold thermal unsensibility resonator is designed and constructed. A maximal output power of 12.9 W at 532 nm wavelength is obtained under a pump power of 30 W with an optical-optical conversion efficiency of 43%. The long term intensity fluctuation over 3 hours free-operation and the beam transfer factor M2 measured at the output power of 11.7 W were less than ±0.83% and 1.5, respectively.