The purpose of this paper is to compare the incentive efficiency of common agency and exclusive dealing, and to examine the influence of the correlations of two tasks on the choice of the two typical agency modes. By establishing a model with two principals and one agent, this paper solved the agents＇ efforts to different tasks, and calculated the principals＇ residuals under common agency and exclusive dealings. The main findings of this paper show that the incentive of the easier task is more efficient, and the principal whose task is easier is more inclined to ＂common agency＂, but the inclination of the other principal is decided by the compliment degree of the two tasks. These findings were aoolied to the compensation system of the faculty in Research-oriented University