The humanity of coding design for human-machine display interface in the product design is studied by experimental method. During the experiment, three character types, three eye distances from the display interface, five character sizes are adopted. The correct rate and reaction time are chosen as the evaluation indexes. Analyzed by ANOVA, mathematical models of the information coding are established. Mathematical models proposed in this paper can be widely applied for man-machine display interface coding design, and provide theoretical basis for different kinds of products design.