We analyze operating characteristics of CW intracavity singly-resonant optical parametric oscillator（ICSRO）theoretically.Furthermore,using the quasi-phase-matched periodically poled MgO-doped lithium niobate crystal（PPMgLN）as the nonlinear converter,we have accomplished low threshold and highly efficient ICSRO,driven by compact and efficient diode-end-pumped CW Nd∶YVO4 laser.The threshold of ICSRO system is only 3.1 W at 808 nm.A maximum idle output power of 370 mW and a maximum signal output power of 540 mW have been achieved when the pump power is 5 W and it corresponds to a whole optic-optic conversion efficiency of 18.2%.