Abstract: Since twenty-first Century, the economic ties between mainland and Taiwan, Hong Kong, Macao have become closer. However, the current situation of one country′s “four currencies” has seriously hindered the integration and development of the four regions. Based on the theory of optimal currency area, a state space model is used to investigate whether the four places in China have the economic base to construct optimal currency area, finding that there is a mechanism for endogenous effect of optimal currency area between mainland China and Hong Kong area, Macao area, and they are suitable for construction of optimal currency area; there is no a mechanism for endogenous effect of optimal currency between Taiwan area and mainland China and they are not suitable for construction of optimal currency area.

Key words: four sides across the Strait, economic cycle, economic shock, optimum currency area, endogenous theory