Abstract: A high-voltage X-ray tube with a mini focal spot is developed, and the high-voltage structure, focusing system, and heat dissipation of the X-ray tube are designed and simulated. At tube voltage 200 kV, the maximum field strength is 17.9 MV/m between the anode and cathode, the focal spot size is 100μm, the resolution is 10 LP/mm, and the maximum operating power is 150 W. When applied to an X-ray counting system, the boundary of 01005 electronic components can be clearly distinguished at a magnification of 2 times.