Abstract: Mn_1-xFe_xCoGe_1.02(x=0,0.01,0.03,0.06,0.09) alloy was prepared by arc smelting method using Fe to replace part of Mn in MnCoGe_1.02 alloy, and the phase composition, crystal structure, martensitic transformation and magnetothermal effect of the alloy were studied.The results show that after replacing part of Mn with Fe, the lattice parameters and cell volume of the alloy basically showed a decreasing trend with increasing iron content. MnCoGe_1.02 alloy at room temperature showed a coexisted structure with orthogonal martensite phase and hexagonal austenite phase. The alloys with x=0.01 and x=0.03 were both single orthogonal martensite phase structure. The alloys with x=0.06 and x=0.09 were both single hexagonal austenitic phase structure. The temperature of martensitic transformation increased first and then decreased with increasing Fe content, and the alloy with x=0.03 had the highest transformation temperature. The addition of Fe effectively improved the intensity difference of magnetization of the alloy. The alloy with x=0.03 had the largest intensity difference of magnetization, and at 5 T and 315 K, the alloy had the largest magnetic entropy change of 18.7 J·K^-1·kg^-1, indicating that the alloy had the relatively large magneto-thermal effect.