For transactions’ mobility and the inherence limitations of wireless network, traditional real-time transaction management mechanisms are incompetent to support the execution of mobile distributed real-time transactions in mobile distributed computing environment. In this paper, the commit mechanism for mobile real-time transactions is studied. First, a nested transaction model based on functional alterative tasks is given by analyzing the characteristics of real-time transactions in mobile distributed environment. Then a three-tier commit structure supporting the suggested model is presented. And a three-phase real-time commit protocol 3PRTC (three-phase real-time commit) is also proposed, which can guarantee the atomicity and structural correctness of the mobile real-time transactions. By performance testing, it is shown that the suggested transaction model and its commit mechanism can improve the successful ratio of real-time transactions.