According to requirement of the actual laser system, a design scheme of a continuous phase plate (CPP) for laser beam with random phase distribution has been developed. A kind of method has been established to analyze the smoothing character of CPP. The random theory is employed to study the statistic characteristics of the laser beam. The propagation parameters have been calculated and the results show the far-field distribution of the laser beam. Using the design principle, a CPP that can be used in the actual light path is designed and its surface character is analyzed in detail.