The basic structure of 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 x ray collimator for radiography, and the positioning lamp is characterized in that the positioning lamp is a light emitting diode. At present, the new type of light-emitting diode is used as positioning lamp. Compared with the original halogen lamp as positioning lamp x ray collimator for radiography, the new type of light-emitting diode has the following advantages: (1) low power consumption, can greatly reduce the power consumption of the x ray collimator for radiography, high efficiency and energy saving, especially suitable for portable X-ray generator; (2) high brightness of light-emitting diode and clear irradiation area. (3) Light emitting diode (LED) 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 LED, locate for a long time, and the positioning effect is better, and the positioning operation is more convenient.