An accurate method for measuring the chip temperature of semiconductor lasers is presented. Because the heat capacity of semiconductor laser is very small, using pulse injection can reduce temperature rising significantly. First, the change of environment temperature versus lasing wavelength under pulse injection is discussed, and the relationship between the lasing wavelength and the width and cycle of injection pulse is obtained. The measured relationship agrees well with the calculated one. Based on this relationship the optimum parameters of the pulse for measuring the chip temperature of laser diode (LD) are obtained, viz. pulse width is 10 ns, pulse cycle is 10 μs. The definite relation between lasing wavelength and chip temperature is developed, and the drift coefficient is 0.0728 nm/K. This method avoids junction voltage overshoot in electricity measurement, and it is more accurate than the latter. This method is also convenient for measuring temperature character of packaged laser unit.