This article introduces the implementation of an 8-bit high performance network microcontroller. This chip is mainly composed of an 8-bit embedded MCU integrated with a 10M Ethernet MAC. A two-stage pipeline and ESFR (external special function register) method are adopted to design a high performance MCU. The architecture, features and main modules realization of the chip are discussed in the paper. The chip is fabricated using 0.25 mum CMOS technology and the die size is 2.6 times 2.6mm2. Some successfully developed applications based on this network microcontroller are also presented in this article