In this paper, the quantitative function of the short-time temperature rise rate of LED is deduced theoretically without considering the heat dissipation from the LED devices to the surrounding environment. A new idea and method for measuring the temperature rise rate of LED in a short time is proposed experimentally. Moreover, the relationship between the temperature rise rate and the change of power-on time, current and junction temperature is studied, and the importance of device heat dissipation is qualitatively discussed. The results show that when the terminal voltage and current of the LED are constant, the temperature rise rate of the LED is independent of time in a short time; when the junction temperature of the LED is constant, the temperature rise rate changes linearly with the current; when the current passing through the LED is constant, the temperature rise rate increases first and then decreases with the increase of junction temperature, and reaches the extreme value when the junction temperature is 60℃. Therefore, it is recommended that the temperature should be lower than 60℃ so as to ensure the good heat dissipation of LED device.