In the wavelength range of 231-275 nm, we have studied the mass-resolved dissociation spectra of OCS＋ via B2∑＋←X2П3/2（000） and B2∑＋←X2П1/2（000, 001） transitions by preparing OCS＋ ions in the well-defined spin-orbit states. The spectroscopic constants of v1 （CS stretch）=828.9 （810.4） cm-1, u2 （bend）=491.3 cm-1 and v3（CO stretch）=1887.2 cm-1 for OCS＋（B2∑＋） are deduced. The observed dependence of the v2（bend） mode excitation of B2∑＋ on the spin-orbit splitting of X2П（Ω=1/2, 3/2） in the B2∑＋←-X2П transition can be attributed to the K coupling between the （000）2П1/2 and （010）2∑＋/2 vibronic levels of X2П state, which makes the B2∑＋（010）←X2П1/2（000） transition possible.
