The MnBi/Sm₂Co₁₇ composite powder was prepared by chemically assisted high-energy ball milling process, and the effect of the content of MnBi alloy on the magnetic properties and microstructure of the composite powder has been studied. As the content of MnBi alloy increases, the coercivity of the composite powder first increases slightly, and then keep stable at about 8.0 kOe, while coercivity of all the composite powder was lower than 10.8 kOe of pure MnBi milled powder; the saturation magnetization and remanent magnetization of the composite powder gradually decreased. No obvious elements interdiffusion was found in the composite magnetic powder. The exchange coupling effect of the composite powder was analyzed by the Henkel curve. The δM of the composite magnetic powder reaches the maximum value when the MnBi addition amount was 15wt.%, indicating that the composite powder has a strong exchange coupling effect. The evolution of the remanence ratio of the composite magnetic powder with the increase of MnBi alloy content has been analyzed depending on the morphology and the exchange coupling effect of the composite magnetic powder.