The basic structure of beam x ray collimator includes shell, positioning lamp, mirror and open limit structure. The positioning lamp, the mirror and the open limit structure are installed inside the shell of the beam x ray collimator, and the positioning lamp is characterized in that the positioning lamp is a light emitting diode. At present, a new type of positioning lamp using light-emitting diode as beam x ray collimator has many advantages compared with the original one using halogen lamp as beam limiter. For example, the light-emitting diode of LED lamp has many advantages, such as low power consumption, can greatly reduce the power consumption of beam limiter, high efficiency and energy saving, especially suitable for portable X-ray generator. Clear radiation area is conducive to the rapid positioning of the X-ray irradiation area; the light-emitting diode has very small calorific value, even if it is lit for a long time, it will not cause the shell and other devices to overheat, so it can prolong the light-up time of the light-emitting diode, long-time positioning, better positioning effect, and more convenient for the positioning operation of the beam x ray collimator.