In FM screening techniques, using pseudo-random generator to ensure exposure dots is a method to generate screen dot. Dots generated by traditional algorithm scatter greatly which leads to dot gain and cannot accurately reproduce manuscript's color and tone. On the basis of traditional algorithm, this paper brings forward a multiplicative congruence pseudo-random algorithm based on dot gathering model. It firstly puts forward the modeling thought and screening project, and then sets multiplicative congruence pseudo-random algorithm as basic model to ensure pseudo-random number generator. On the analysis of dot data, it sets up the dot gathering magnitude model according to pixel grey level. Then coordinate system on the halftone unit is set up to ensure dot coordinate. Finally, dots are generated. By designing screening experiment, it compares this algorithm with traditional ones and evaluates the quality of halftone images and printed images respectively. Experiment testifies that this algorithm has the advantages of FM screening, whose printing characteristics are better than traditional AM screening and dither screening.