To meet the requirement of high efficient SHG,using a colliding pulse modelocked(CPM)Nd:YAG pulsed laser with a convexantiresonant ring(ARR) unstable resonant and LBO,BBO crystals as intracavity doubler,an efficient SHG with energy conversion efficiencies of 65.3% and 43.6% are demonstrated,respectively.The experimental result also shows that ISHG can have an interesting effect of stabilization in the output power of a pulsed laser with a decrease of energy fluctuation from 3.6% in the fundamental wave to 2.4% in SHG.Meanwhile.