The investigation of the thioxophosphine (PS) formation from different reaction paths is successfully performed and presented in this paper. The PH(3)+SH(1) reaction is likely to yield the intermediates PH(2) (2)+H(2)S through an energy barrier of 2.8 kcal mol(-1). However, the next step is the H(2)PS(2) formation, which has a too high energy barrier, 52.6 kcal mol(-1). The PH(3)+S(1) reaction path is the likely source of the HPS(1) molecule. The other possibilities are the PH(1)+H(2)S, PH(2) (2)+SH(1), and PH(3)+H(2)S reactions, but they are spin forbidden and energetically unfavorable for the HPS(1) and PSH(1) formations. On the other hand, the PS(2) formation is more likely to happen by the PH(1)+SH(1) reaction. The PH(2) (2)+S(1), PH(3)+SH(1), P(2)+H(2)S, and P(4)+H(2)S reactions are also favorable in terms of energetics; however, these reactions are spin forbidden. The chemical mechanism for the PS(2) formation is now presented in more details, which is of great importance in the atmosphere of Jupiter and Saturn, and in interstellar medium.