In this paper, we o introduce the Reusable Embedded In-Circuit Emulator (EICE) and Reusable EICE development system. The main function in EICE we design are testing and debugging. The architecture of EICE is reusable and based on IEEE 1149.1 boundary scan architecture. The EICE development system can help EICE to reduce developing time while developing a microcontroller/microprocessor. We implemented EICE by ASIC and FPGA way and the development system had been demonstrated in two microcontroller.