This paper introduces the trigger system of the middle energy X-ray device and experimental results. The trigger system controls triggering of laser-switches in six modules and the electric trigger part. Each switch is triggered by one laser. Seven lasers could be adjusted stand-alone. The test results show that the time jitter of laser was less than 0.3 ns and the time jitter of the laser-switch was less than 1.2 ns. For electric trigger system, the voltage of the matching load was 120 kV, the rising time was about 28 ns, the pulse width (FWHM) was 150 ns, and the time jitter was less than 0.5ns. The middle energy X-ray device could produce a maximum output voltage and current of about 4.2 MV /100 kA and the pulse width (FWHM) was 150 ns. The time jitter of X-ray was less than 3.4 ns in the middle energy X-ray device. The experimental results show that the trigger system was able to adjust the six modules accurately, which improves reliability of the middle energy X-ray device.