Conventional semiconductor laser threshold extraction method can be affected by noise, poor reproducibility. Under the principle of singularity detection of wavelet transform, it is proposed that wavelet transform is adopted for threshold current extraction, which uses third-order spline function as a double expansion smooth , taking its second derivative for the wavelet function , and multi-scale integration. Experimental results show that compared with several traditional methods, such as the two-segment line fitting method, first derivative method and second derivative method, the method based on wavelet extraction is not susceptible to noise and can truly and accurately obtain the threshold current of semiconductor lasers.