The 18 -S states correlated to the lowest dissociation (Si(3Pg)+S(3Pg)) limit are computed with high-level multireference configuration interaction (MRCI(SD)) approach through utilizing all-electron aug-cc-pwCVQZ-DK basis set. The scalar relativistic effect and the core-valence correlation effect of Si (2s22p6) and S (2s22p6) are taken into account. On the basis of calculated potential energy curves, the spectroscopic constants of the bound states are fitted, including equilibrium distance Re, adiabatic transition energies Te, harmonic vibrational frequencies e, anharmonic terms exe, and rotational constant Be. The electronic configurations at different bond lengths are given. The electronic dipole moments of 18 -S states are calculated, illuminating the influence of electronic configuration variation on electronic dipole moment. With the help of nonvanishing spin-orbit matrix elements including b3 and A1 as a function of the internuclear distance, the nearby state perturbations to b3 and A1 are discussed in detail. Finally, the transition dipole moments and Franck-Condon factors of A1X1+ and E1+X1+ transitions are obtained, and radiative lifetimes of five lowest vibrational levels of the two singlet excited states are evaluated.