Abstract: Hollow structures fabricated by 3D printing have important engineering significance in weight reducing. Using X-ray computed tomography (CT) technology.This paper is concerned with the problem of non-destructive testing of 3D printed hollow structure with photosensitive polymer resin is studied. By studying the effect of X-ray tube voltage and current on the signal-to-noise ratio, sharpness and contrast of CT images, the optimized parameters for the experiments were obtained. The defect size were measured non-destructively in the acquired CT images. The non-destructive tested results were verified by destructive testing, and the measured error was analyzed. The results show that the testing sensitivity and accuracy can be improved effectively by using the optimized testing parameters. Under the experimental conditions, the gas pore with a diameter of 0.1 mm can be identified, and the size of the defects can be measured with an average relative error of 16%.