FeCoCrNiB high-entropy alloy coating was prepared on the Q235 steel substrate. The coating is free of crack and pore defect, which is composed of rod-like M₃B phase and fcc matrix phase. Formation mechanism of the phases was analyzed. Effects of high temperature annealing on microstructure and microhardness were investigated. The results show: after annealed at 900 ℃ and 1000 ℃ , some granular and short rod-like M₃B phase are precipitated in coating; After annealed at 1150 ℃ , rod-like, granular and short rod-like structure disappear, a blocky M₃B phase formes, the microhardness of blocly phase is 1188 HV; The coating exhibits excellent resistance to high temperature softening, the decrease of microhardness is only about 7 % and 9 % after annealed at 900 ℃ and 1000 ℃ .