A new method to improve laser beam quality by using intracavity phase modulation is presented. The phase modulation is fulfilled by LiNbO 3 electro optic crystal driven by high voltage. The laser used is CW Nd:YAG solid state laser pumped by Krypton lamps. The experimental results show that intracavity phase modulation can transfer effectively the laser oscillation mode from multi mode to fundamental mode like beam with smooth intensity profile.