For the first time, the spectroscopy and transition properties of SeCl + are systematically reported. The potential energy curves of 22 Λ − S states and the corresponding 51 Ω states in the first and second dissociation channels of SeCl + are calculated using the internally contracted multiconfiguration interaction and Davidson correction method. The phenomenon of avoided crossing in Ω states below 30,000 cm −1 is discussed in detail. The spectroscopy constants are obtained by fitting the potential energy curves, and also the Franck− Condon factors and radiation lifetimes of the X 3 Σ 0 + − ↔ 2 1 Σ 0 + + transition are calculated. Between X 3 Σ 0 + − and 2 1 Σ 0 + + , the Franck−Condon factors are large, close to 1, but the radiation lifetime is large too. According to the calculation results, it is determined that direct laser cooling of SeCl + is considered infeasible.