It is depended on the experience to identify the screen line and angle for the print products. In this paper, We designed the screen directions determiner according to the principle how the Moire Fringe produced. An example of serial screen line 85,100,120,133,150,175,200Lpi is given, and a method of design is proposed for Suitable screen angle and output points of laser phototypesetter. Analysis of quantization about screen line and angle for the print products are discussed. At the same time, It is derived from Moire formula and the dot transmittance Equation. The result has an important guiding significance for printing practice.