PC-type CdS detector is irradiated by 532 nm in-band and 1319 nm out-of-band continuous wave (CW) lasers simultaneously. The voltage responses are recorded when the power of the two laser beams changes separately. It is shown that the detector responses to the irradiation of both in-band and out-of-band lasers, but the response to the irradiation of out-of-band laser is opposite to that of in-band laser. The voltage response to the out-of-band laser increases with the rise of line-working in-band laser power and decreases rapidly while the in-band laser power approaches to the saturation threshold. Analysis shows that the response to the out-of-band laser is related to laser excited hot carriers, which is due to the carrier absorption of the incident photons resulting in an intra-band transition. In-band laser irradiation has an effect on the absorption coefficient of the out-of-band laser.