Ab initio calculation on the low-lying excited states of BCl radical

► This is the first time that the MRCI + Q method has been used and SOC effect has been evaluated for BCl. ► The quintuplet electronic states of BCl radical are reported in our work for the first time. ► Spectroscopic constants for the 3Π(III), 5Π(I), 3Σ−(II) and 3Π(IV) are firstly reported. ► Complete potential energy curves of 22 Λ-S electronic states and 6 Ω states are depicted. ► The dissociation energies of the calculated electronic states are predicted in our work..