Light reduction experiments were carried out with a 488 nm continuous laser under the same exposure. Simultaneously the properties of reduced graphene oxide (rGO) were characterized by transmittance and resistivity. The results show that during the reduction process, the degree of reduction characterized by resistivity and transmittance presents the same trend. Moreover, the reduction process is divided into two steps: before reaching the relatively stable state and reaching the relatively stable state. Before reaching the relatively stable state, the lower the laser power density, the higher the reduction degree of the samples; but when reaching the relatively stable state, the higher laser power density, the higher the reduction degree of the samples. This phenomenon is further analyzed by means of photon penetration and bandgap modulation, based on the change of oxygenated functional groups in rGO.