The present disclosure provides an X-ray generator with adjustable collimation. The X-ray generator comprises: an assembly of X-ray source, which includes an X-ray tube having a cathode and an anode and a front collimator; a high voltage generator, which is disposed in an extended chamber of a housing for the X-ray tube and which is used for supplying a direct current high voltage between the cathode and the anode of the X-ray tube to excite X-ray beams; a collimation adjustment unit, which is rotatably disposed outside of the front collimator and which is used for adjusting fan-type X-ray beams into continuous pencil-type X-ray beams; and a cooling unit, which is independently mounted to the X-ray tube and which is used for cooling the anode of the X-ray tube; wherein, the assembly of X-ray source, the high voltage generator, the collimation adjustment unit and the cooling unit are integrated as a whole. The X-ray generator with adjustable collimation according to the disclosure has a compact construction, which is helpful in miniaturization, modularization and high efficiency of a security detection equipment.