Two kinds of semiconductor lasers (InGaAs, 2 W, continuous output, infrared 980 nm and InGaAsP, 120 mW, continuous output, infrared 980nm, including tail-fiber and cooler) are taken for examples and the rules of the change of semiconductor lasers output wavelength correspondig to operation current are experimentally investigated. The results show that the emission wavelength of the laser shifts in the direction of long wavelength as the operation current rises. The slopes are approximately 0.374 nm/100 mA and 0.220 nm/10 mA, respectively. Furthermore, the change of wavelength becomes more obvious while laser works in large current.