With the development of wireless network technology, the Wireless Fidelity (Wi-Fi) technology has been widely used in areas such as communication and control. Based on embedded Web server and the Wi-Fi technology, this paper designs and develops a multi microcomputer protection and control device for RMU. It takes the Web server/browser mode as the human-computer interaction. Using a Tablet PC, people can access to the LAN via Wireless Wi-Fi connection and then do some operation such as protection parameter settings. Compared with the traditional way of LCD screen/key, it is more comfortable and convenient, and more suitable for the using in a closed hot environment such as the RMU in the summer. This paper detailedly introduces the embedded Web server, the Wi-Fi technology, the Asynchronous JavaScript and XML (AJAX) technology, the network encryption technology and other key technologies in the application of microcomputer protection devices. This work is supported by National Key Research and Development Program (No. 2016YFB0900400 and No. 2016YFB0900403).