Four FeCrCoMn high-entropy alloy coatings with different preset body sizes are prepared on the surface of 45 steel substrates by laser cladding technology, and the effect of preset body size on the corrosion performance of the coatings is analyzed. The results show that the phase composition of samples with various preset body sizes are all FCC and HCP solid solution structures. However, the microstructure and morphology of the coating are transformed from equiaxial crystals to columnar dendritic crystals with the increase in the preset body size and the size of more than 10-mm grains coarsen obviously, which results in the gradual decrease in hardness and aggravation of the abrasion. The corrosion mechanism of the coating is mainly pitting, and the wear mechanism is mainly abrasive wear, adhesive wear and corrosive oxidative wear. With the increase in the preset body size, the corrosion and abrasion resistance of the coating increases first and then decreases. When the preset body size is 15 mm, the coating has high corrosion protection efficiency due to the dense structure of the coating and few solidification defects, which makes the coating show excellent corrosion and abrasion resistance.