Abstract: To gain the analytic solution of interaction between half-space and orthotropic rectangular middle thick plate, two equations were combined. One is the displacement control equation of orthotropic rectangular middle thick plate and the other is the plate-ground deformation compliance equation based on the integral solution of the elastic half-space loaded with arbitrary vertical force. Using the method of trigonometric series, the analytical solution was obtained to describe the characteristics of the orthotropic rectangular middle thick plate with four free edges on the elastic half-space, including the reactive force of the ground, the deflection and the inner force of the plate, etc. Some computational examples were presented. The results fit well with those appeared in literatures. The method proposed in this paper would be of important practical applications.