The characters of proton exchanged(PE) LiTaO3 optical waveguides are studied and the Cerenkov second harmonic generation (CSHG) from 1.064 μm to 0.532 μm is demonstrated the in these waveguides with a conversion efficiency of 122 %/W. cm2.The quality of the harmonic beam is high and the beam divergences along the two directions of vertical and parallel to the plane of the waveguide are 1.3 and 3.3 milliradian respectively.