Abstract: Based on the analysis of Ovation alarm function of digital I＆C system in nuclear power plants and the simulation requirements of virtual control system, this paper has designed an alarm software specifically for the virtual control system. This software takes the operation results of control function module in the virtual DPU server as the source of the alarm information, and it applies the socket communication model to realize the transmission of the alarm information, and Active X controls have been used for real-time interaction of the alarm display screen. The alarm software can simulate the main features of Ovation alarm system in nuclear power plants, therefore it can provide strong support for training the operators and improving the ability to deal with the fault process in nuclear power plants.