In this work, by using first principles calculations, a new two dimensional structure namely SiP2S monolayer with rectangular atomic configuration is theoretically predicted. Our simulations proved that SiP2S monolayer indicates a good stability suggests its promise for experimental realization. Exploring the electronic properties shows that the proposed monolayer is an indirect semiconductor with a moderate band gap of about 1.19 eV calculated by HSE06 level of theory. Optical properties calculations show that this monolayer exhibits good absorption in low energy region of the electromagnetic spectrum. These results propose this new monolayer as a promising material for opto-electronic devices.