A gengral theoretical research of continuous wave KTP optical parametric oscillator (cwOPO)is taken. Based on conservation of energy and momentum respectively calculation of phase match,effective nonlinear coefficient,walkoff angle,acceptance angle,conversion efficience,and threshold were set forth. At the same time,the impact of the phasemismatch,the crystal length,and the output couple′s reflectivity on the conversion efficiency and the threshold of a cwOPO was analyzed. This paper is of some reference value to the design and optimization of continuous wave KTP optical parametric oscillator.