Herein， a method based on Scanlab is proposed to satisfy the technical stability requirements of special collimating light sources. The relation between the angle of incidence and transmittance is used as the principle of signal regulation. A quartz plate is fixed with Scanlab， and the transmittance of quartz is adjusted when Scanlab rotates. Real-time data feedback is recorded using a monitoring detector. To achieve power stability of the light source， the rotation angle， transmittance parameters of quartz， and angular range are analyzed based on Fresnel's law. A proportional-integral-derivative algorithm is used to modulate the error in the signal of the monitoring detector and the voltage corresponding to the reference power to accurately adjust the output of Scanlab. A stabilizer is used to control the power of a He-Ne 632.8 nm laser， and a trap detector is used to verify the level of power stability. The experimental results pertaining to the stability of the laser after modulation are as follows： The standard deviation CV is 0.016% （1 800 s）， and the peak-to-peak fluctuation SV is ±0.042% （1 800 s）. Compared with the free-running result， SV and CV are improved by factors of 8.79 and 13.76， respectively， and the power stability of the laser is enhanced.