Traditionally, bulky external vacuum pumps are used to obtain and maintain vacuum state of the high power microwave system, which significantly increase the size and weight of the system, and limit its practical application. To achieve lightweight and miniaturization of the high power microwave system and improve its practicality, a vacuum-sealed device is designed for X-band repetitively pulsed high power microwave system. Ceramic-metal brazing technology is used at the interface between the pulse transmission line and diode, as well as between the horn mouth of the microwave antenna and the air, while knife-edge sealing technology is used at other interfaces of the system, thus to achieve vacuum packaging inside the high power microwave generation, transmission, and emission cavity. By using methods of vacuum acquisition in the field of vacuum electronics, such as material surface cleaning and baking, the system can maintain a pressure of the order of 10^-7 Pa for nearly 100 h in non-operating conditions. The non-evaporable getter pumps are installed on the cylinder of the diode and the horn of the microwave antenna, which can effectively capture the gas released in the cavity when the system is powered up and maintain vacuum dynamically. The experimental results show that the system can run more than 10 000 shots stably at the pulse repetition frequency of 10-30 Hz.