According to the alarm system of digital I & C system(Teleperm XP) for nuclear power plant, an alarm system is developed for TXP virtual machine used for the training of nuclear power plant operators, which takes the ASD(Alarm Sequence Display) as the simulative object and adopts the technologies on open Windows platform: SQL database management, JavaScript, Visual C++ programming and ADO data access. TXP virtual machine has the client/server system structure, and the ASD consists of the overview area and the page area, represented on CRT with the functions of alarm overview, selective display and classified display. The simulated alarm system completely reproduces the real alarm system in TXP virtual machine.