In recent years, micro-processors have been applied to embedded systems and portable devices widely. Most embedded systems do not require very powerful capability of process which means that it only needs higher adaptive, expansive and transplantable systems. Under above demands, 8051 micro-processor sets have been put in use on many applicative devices. However, finite I/O ports in 8051 micro-processor truly put restrictions on its network applications. Our topic in this paper is mainly improving the lack of I/O ports in 8051 micro-processor and developing the applications to Ethernet network. We design two different kinds of circuits called “RAMx Interface Circuit” and “Ethernet Interface Circuit” to help combine several systems. Further, modifying the internal architecture of 8051 micro-processor with multiple I/O controllers is another important implement in our research. To connect to Ethernet network through 8051 micro-processor, we join 8051 micro-processor with multiple I/O controllers to Ethernet Interface Circuit, and our system enable us to control Ethernet controller through memory- mapping I/O. Finally, we materialize RAMx Interface Circuit and Ethernet Interface Circuit on FPGA board.