The effects of ultrasonic vibration fields with different amplitudes on the microstructure and mechanical properties of laser cladding Fe- V-Cr Fe-based coatings on 304 stainless steel were studied. The results show that due to the cavitation effect of ultrasonic, the grain can be refined effectively and the CET (Columnar to equiaxed transition) transition at the interface can be promoted, and the microstructure inhomogeneity can be improved. The columnar crystal lengths were 42.2 μm, 32.7 μm and 8.1 μm, respectively, under the condition of no ultrasonic application and ultrasonic application (amplitudes of 35 μm and 50 μm), which greatly reduced the width of columnar crystal region and promoted the precipitation of vanadium carbide (VC). Without ultrasound, the microhardness gradient is larger, and the microhardness difference is up to 162.7 HV, while the microhardness is more stable and the hardness gradient is smaller under the ultrasonic condition of 35 μm amplitude, and the microstructure of the cladding layer is more uniform in all directions. When ultrasonic vibration field with amplitude of 35 μm and 50 μm is applied, the tensile strength is 1279.3 MPa and 1162.6 MPa respectively, which is 28.6% and 17.0% higher than that without ultrasonic vibration field applied.