When operating at a high-power region,thermal lens effect of diode pump solid state laser is an important factor which must be considered to optimize the laser system.The Nd:YVO₄ crystal is pumped by a fiber-coupled laser diode which is shaped and focused by a lens group.The focal length of thermal lens is measured by using stable cavity method.The mode distribution of three thermal stable resonators with the thermal focal length is simulated by LAS-CAD software.By using this results the LD dual-end-pumped Nd:YVO₄ laser Z-folded resonator has been optimized,with total reflection mirror radius of curvature R1=300 mm,and output coupling mirror radius of curvature R2=100 mm,with length of the resonator Ltotal=280 mm,and transmisttance of the output coupling mirror T=50%.CW TEM00 mode output is 21.3 W when the pump power is 61 W,and beam quality factor M2 is less than 1.41.The experimental results on laser output characteristics are in good agreement with the theoretical ones.