X射线成像系统点扩展函数是影响X射线成像空间分辨率和密度分辨率的决定性因素,在系统分析X射线成像物理过程基础上,建立了X射线成像系统点扩展函数的一种数学解析模型,推导出了射束有效宽度计算公式,最后通过实验验证了模型的正确性。该模型为X射线成像系统空间分辨率和密度分辨率的初步设计和评定提供了理论依据,可作为X射线图像恢复算法中模糊函数的先验信息。 The point spread function of X-ray imaging system is the decisive factor that affects the spatial resolution and density resolution of X-ray imaging system. Based on the systematic analysis of X-ray imaging physical process, a mathematical analytical model of point spread function of X-ray imaging system is established. The calculation formula of beam effective width is deduced. Finally, the correctness of the model is verified by experiments. The model provides a theoretical basis for the preliminary design and evaluation of the spatial resolution and density resolution of the X-ray imaging system and can be used as the prior information of the ambiguity function in the X-ray image restoration algorithm.