The invention discloses an X-ray collimator and belongs to the technical field of medical diagnosis equipment. Two sets of driving devices can drive to realize three functions of adjusting widths of ray fan beams, adjusting a central position of the ray fan beams and switching filters. A first driving device drives a ray fan beam width adjusting mechanism, and a second driving device drives a ray fan beam central position adjusting mechanism and a filter switching mechanism respectively. Due to the adoption of an arc-shaped gate bent into an arc surface, distances from all points of the collimator to a focus of a ray source are the same; and when the slit width of the collimator in an overall length range is fixed, ray fan angles in the whole light field range are equal, the controlled widths of the ray fan beams are equal, and the collimator contributes to improvement on image quality. The filter has a blocky structure with a parabolic curved surface; and when rays pass through the filter, attenuation degrees of ray energy are different due to different pass-through distances, so that the requirement of scanning different tested objects is met.