The 21^st Century Maritime Silk Road is a regional cooperative mechanism and it will provide public goods for the countries in the region. The 21^st Century Maritime Silk Road is a process with the features of joint building，sharing and openness. Joint building of the 21^st Century Maritime Silk Road means countries in the region share the responsibilities of providing public goods while China as a big country may provide bigger share of public goods and share the public goods with countries in the region. As an open mechanism，the 21^st Century Maritime Silk Road welcomes other countries to join the “club” to share the responsibilities and obligation. As a new mechanism，the 21^st Century Maritime Silk Road is faced with 7 problems，including：the high trade volume between China and the countries along the Maritime Silk Road，the trade imbalance between China and the countries along with Maritime Silk Road，low level of institutionalization，easily effected economic relations by political or security relations，failed states along the Maritime Silk Road，piracy in the Indian Ocean，and difficulties in connectivity. These problems represent the necessity and difficulties of Maritime Silk Road. The construction of the cooperative mechanism for the 21^st Century Maritime Silk Road includes five platforms：trade promotion and trade disputes settlement platform，connectivity platform，finance platform，official development aid platform，and foreign investment platform. The elevation of Cooperative Mechanism for the 21^st Century Maritime Silk Road can be achieved from the dimensions of effectiveness and legitimacy.

The 21^st Century Maritime Silk Road is proposed by China and should be beneficial for the national interests of China while it is worth noticing that the interests of Maritime Silk Road as a cooperative mechanism are not necessarily identical with China’s national interests. With the increase in the number of members of the Maritime Silk Road，the dilemma between effectiveness and legitimacy will become significant which requires more delicate design.