Anion photoelectron spectroscopy and theoretical calculations were used to investigate the structural, electronic, and bonding properties of BS⁻ and BS₃⁻. Vibrationally resolved photoelectron spectra of BS⁻ at 355 nm and 266 nm were obtained. The electron affinity of BS is determined to be 2.32 ± 0.05 eV. The stretching vibrational frequencies of BS⁻ and BS were measured to be 968 cm⁻¹ and 1210 cm⁻¹, respectively. The results indicate that the B–S bond in BS^−/0 can be characterized as a triple bond. The B–S bond in neutral BS is stronger than that in anionic BS⁻. The most stable isomer of BS₃⁻ has a C_2v symmetric planar structure with the B atom at the center interacting with the three S atoms, while that of neutral BS₃ has a S–B–S–S bent structure.