The electrical low-frequency noise of 976nm InGaAs quantum well high-power semiconductor lasers was measured under a current less than 1/30 of the threshold current. An approach was proposed to analyze the noise origins by using the relation between the 1/f noise correlation of time-domain signal wavelet coefficients and the bias current. Combining the 1/f noise origin model with the characteristics of the wavelet coefficients, a series of contrast experiments were conducted to compare the results before and after adding white noise under different bias currents. The results indicate that, the low-frequency noise we measured shows typical 1/f noise characteristics. For a pure 1/f noise, the same results are obtained when to determine the noise origin by using the noise amplitude method and wavelet coefficients correlation method. However, for the 1/f noise signal containing white noise, there is a significant fluctuation on the noise amplitude and it cannot show the origin 1/f noise correctly, whereas the wavelet coefficients correlation under some scales is still a reliable criterion.