The experimental results of KTP optical parametric osillator(OPO) pumped by Nd:YAG lasers are reported at both wavelengths 1064 nm and 532 nm with critically phase-matching (CPM) and non-critically phase-matching (NCPM). The eye-safe lasers have been demonstrated with tuning range of 1.53 to 1.84 μm, maximum energy of 130 mJ, and energy conversion efficiency as high as 64%. The tuning range, walk-off angle, acceptance angle, threshold and conversion efficiency are compared and analyzed, and the effects of walk-off on the beam quality and conversion efficiency of OPO are discussed.