Abstract: Using two basic performance measures (i.e.schedule variance and cost variance) in the EVM system,this paper builds a multi-task principal-agent model for project management,and provides an approach to calculate the contract parameters.Further,it gives the relationship between the incentive intensities for different kinds of efforts: when the agent's efforts are substitutes (complements),the corresponding relationship between incentive intensities is substituting (complementary).Finally,it analyzes the impacts of exogenous parameters on the degree of substitution (complementarity).The result shows that the degree of substitution (complementarity) increases as the degrees of the agent's substitution (complementarity) between two kinds of efforts,the magnitude of his/her risk aversion,and the marginal relative risk of his/ her efforts to reduce the actual costs of the project increase,but decreases as the marginal relative risk of his/ her efforts to raise the earned value of the project increases.

Key words: project management, earned value management, multi-task principal-agent contract, incentive