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In this research, optical absorption regulation of Ag nanodisc arrays in a monolayer MoS2 hybrid system is investigated using the FDTD technique. Ag nanodisc arrays are designed on monolayer MoS2 on SiO2/Si and Au/SiO2 substrates. For Ag/1L MoS2/SiO2/Si, two absorption peaks near 620 nm and 670 nm are showed, with different intensification amplitudes of absorption peaks and slight shifts in peak position changing diameters or spacing of Ag nanodiscs. When the diameter is 220 nm, the strongest absorption peak is displayed at 745 nm. When the spacing s is 300 nm, the absorption peak at 759 nm has the highest intensity. When the thickness of the SiO2 film increases from 90 to 280 nm and 300 nm, the intensity of the absorption peak near 620 nm increases by 1.7 times, and the peak blueshifts to 585 nm. In the band from 550 to 700 nm, the presence of the Ag nanodisc array significantly enhances the absorption of the film system, when the thickness of the SiO2 film is 300 nm, and the enhancement amplitude of the absorption peak near 620 nm reaches three times. For Ag/1L MoS2/Au/SiO2, when the diameter or spacing of the Ag nanodisc increases from 100 to 220 nm every 30 nm, the peak positions of 620 nm and 670 nm are changed. When the diameter of the Ag nanodisc is 100 nm and 220 nm, the normalized absorption rates at 686 nm and 707 nm are 0.95 and 0.96, respectively. When the spacing s is 200 nm and 400 nm, the normalized absorption rates at 562 nm and 686 nm are 0.94 and 0.96, respectively. By comparing the optical absorption with and without the Ag nanodisc array, the absorption of the monolayer MoS2 hybrid system is greatly enhanced. When the surrounding medium is changed from air to water, the absorption peaks of 641 nm and 686 nm become 587 nm and 775 nm, the distance between peak positions is enlarged, and the intensity is obviously weakened, which is due to the weakening of the surface plasmon effect of the Ag nanodisc array. [ABSTRACT FROM AUTHOR]