From the perspectives of the three-shortage of the mode of investment and financing，project and capital of infrastructure of China in 2019，this article analyzes the similarities and differences of the inherent logic，external environment，decision making and implementation route of policy between the government special bond and PPP，and accordingly studies on the long term mechanism of the policy of special bond，and advises on its basic positioning，land ideas and mechanism design. From the perspective of policy implementation，the special debt and its supporting policies should strengthen the predictability of the policy and reasonably control the entry threshold of the project；in the aspect of mechanism design supporting the special debt policy，it should return to the internal logic of infrastructure project investment and financing，and seek the supporting mechanism design of “three sets breakthrough”.