Aimed at the problem of the loss of radar detection range and even the damage of transmitter due to the reasons such as environmental factors, aging effects including electronic components, critical parts and so on, the radar transmitter on-line monitoring system is designed. The monitoring system based on embedded Linux operating system is composed of virtual-instrument module and monitoring software, and the core of monitoring system is CPU module based on PC/104 bus. A series of researches show that this system can complete the on-line monitoring including radar equipment transmitter and standing wave coefficient of radar antenna feeder system. It also has many excellence superior to former instrument, including monitoring precision, monitoring method, reliability and so on. It has been successfully used for one type integrated performance monitoring system and proves fine through its outcome.