Each MIDP2 ready mobile device has its own specific operating system, Java Virtual Machine, optional JSRs, and vendor specific classes, which makes important characteristics of mobile devices: multi-platform. There is no standard running environment for mobile software in the multi-platform environment. This paper presents a mobile computing architecture and solutions for multi-platform adaptation. This architecture consists of an installation agent and two mobile computing solutions to accommodate different mobile platforms. This architecture provides a practical and effective way for multi-platform adaptation in mobile computing. The development of mobile application system proves the usability of this architecture. The implementation of the architecture with a mobile application shows a substantial improvement in mobile platform adaptation for mobile computing. With this architecture, the mobile application software can be run on over 90% of mobile devices in the current market.