This paper studies and designs a common interconnection interface between distributed generation and microgrid. The interface is divided into two parts: information interface and power interface. The functions and design methods of the two parts are analyzed. The plug and play interconnection interface between distributed generation and microgrid is presented. Based on the requirements for microgrid operation, five operational modes of the interconnection models are studied. The designed interconnection unit is used to test the different operational modes and switching from one mode to another. These tests also show that the modular design of the interconnection interface model is scalable, technology independent and flexible to meet the needs of interconnection between different distributed generation units and microgrid.