The spin-state transition is an interesting phenomenon in perovskite materials. Using the first-principles DFT method and LSDA+U calculations, we have fulfilled a detailed investigation on the structural and magnetic ground states of strongly correlated perovskites, BiCoO3, LaCoO3 and their corresponding alloys Bi1-xLaxCoO3 (BLCO). We have found that the structural stability of this alloy between tetragonal-AFM-C and rhombohedral-NM undergoes a transition from a tetragonal-phase to a rhombohedral-phase at x similar or equal to 0.345. This structural transition is connected with a spin-state transition from HS magnetic state to LS non-magnetic state. According to this investigation, we have predicted that the La-substitution in BiCoO3 bulk material can improves all properties related to spin state transition in this system. (C) 2018 Elsevier B.V. All rights reserved.