Abstract: This paper considers that the fourth party logistics makes great efforts to integrate logistics resources and the efforts influence the output of the third party logistics.This paper also researches on incentive mechanism of the fourth party logistics subcontract with principal-agent theory,and draws following conclusions:the more powerful the fourty parth logistics,the more great efforts makes;the more powerful third party logistics works harder than those which is weakness;the fourth party logistics gives more incentive payments to the more competitive third party logistics.

Key words: fourth party logistics, principal-agent, incentive mechanism