Abstract: H13 die steel is widely used in the manufacturing industry. Most of the working environment is harsh, and various failure problems often occur on the surface. Therefore, the surface of H13 die steel needs to be strengthened. Based on the preparation of cladding strengthening layer for H13 die steel in the process of ultrasonic-assisted laser cladding, the effect of ultrasonic power on the size and microstructure of cladding layer is investigated. The results show that the wettability of molten pool surface is increased after ultrasonic vibration is applied. The weld surface becomes relatively flat. Ultrasonic vibration makes the distribution of elements in the cladding layer more uniform and the grains finer. The microhardness of the cladding strengthened layer after applying ultrasonic vibration is 21% higher than that without applying ultrasonic vibration. Therefore, applying ultrasonic vibration while repairing the mold with laser cladding can greatly improve various mechanical properties of the mold surface and prolong the service time of the mold.