It is more difficult for real-time transactions in mobile computing environment (MCE) to meet their deadlines than that in traditional distributed computing environment due to the mobility of transactions and inherent limitations of wireless network. It is necessary to study new transaction management mechanisms for mobile real-time transactions (MRTTs) to make more of them successful. In the first of the paper, functional alternative tasks are suggested for important MRTTs in the interest of enhancing their reliability. Then a nested mobile real-time transaction model based on functional alternation is presented. For guaranteeing the relaxed atomicity and structure correctness of MRTTs, a Three-Phase Real-Time Commit protocol (3PRTC) taking the deadlines associated with MRTTs and mobility into consideration is proposed. In the end, the correctness of 3PRTC is proved.¹