With the vigorous development of the Internet, web applications have been widely used on the PC (Personal Computer) platforms. The maturity of the hardware and software platforms of mobile devices and the promotion of the Mobile Internet have brought a great opportunity to the migration of the web applications to mobile platforms. Because of the constraint of the hardware of mobile devices and the diversity of the mobile platforms, the web application engine on mobile devices ought to be a lightweight and cross-platform engine. This paper first analyzes the current development of mobile Web application engine conditions and limitations, and then introduces xFace an independent researched and developed lightweight cross-platform mobile Web application engine, and the details of xFace’s architecture and the main problems it solves. It concludes with a discussion of the future of mobile Web application engine.