Abstract: The target tube is the main structure of the D-D neutron generator to generate neutrons and cool the deuterium target. In order to improve the high neutron flux required for the ⁴⁰Ar-³⁹Ar uranium ore dating irradiation experiment, the cooling structure of the neutron target tube was optimized to make the target tube meet the heat dissipation requirements of the target temperature and improve the neutron flux of the sample irradiation. Through numerical simulation, it was assumed that the deuterium ion beam was distributed according to Gaussian distribution, and the deposited energy after the beam bombards the target was simulated, and the coolant heat transfer reduces the target temperature. The influence of the target tube cooling structure on the target temperature distribution and heat dissipation capacity was analyzed. The results show that the larger the beam spot radius of the ion beam is, the stronger the heat dissipation capacity of the target tube is, and the lower the maximum temperature of the target surface is. When the beam spot radius increases from 5 mm to 10 mm, the maximum temperature of the target surface will decrease by more than one time. The maximum temperature of the target will decrease with the increase of the coolant flow rate. When the maximum temperature of the target is high, the increase of the coolant flow rate can greatly reduce the maximum temperature of the target. When the flow rate continues to increase, the reduction of the target temperature will not be significant. The inlet position of the cooling water has a great influence on the target temperature distribution. The inlet mode with the water inlet direction parallel to the target surface has the best heat dissipation effect on the target, and the maximum temperature of the target surface is greatly reduced, and the distribution of the target temperature is more uniform. The outlet position of the cooling structure has little effect on the target temperature, and the outlet position of the cooling water outlet direction parallel to the target surface can slightly reduce the maximum temperature of the target. A new target tube was prepared according to the actual processing requirements. It is expected that the neutron flux at the sample position can be increased to 2.6 times of the original. In the future work, we will use the developed deuterium target tube to carry out the experimental measurement of high current D-D neutron source irradiation, calculate and verify the neutron flux, neutron flux rate and neutron yield, and further discuss and analyze the design of the target tube.