In this paper, the infrared LED is described in brief, two kinds of thermal detectors and two kinds of photodetectors are presented, their advantages, disadvantages and basic measurement formulas are indicated and the methods and formulas for measuring the radiation intensity of infrared LEDs are explained in detail. Finally, three suggestions are given for the current measurement standard of infrared LEDs. It is particularlly noted that the measurement of the radiation intensity of LEDs by using a thermal detector is firstly proposed in the LED industry.