In this paper, based on the wavelet transform′s singularity detection principle, the transform coefficients at different scales were given to examine output I-V curve and compute the threshold current and other correlative parameters, such as the modular max WM2j and junction characteristic parameter m and so on. Making use of the above examined parameters combining with electrical derivative method, the reliability of semiconductor laser and quality of device can be compared directly and evaluated accurately. The theory and the experiment indicate that compared with the other classic methods, this method is distinct.