Abstract: Researches on the laser deposition repair of BT20 alloy forgings having defects mis-machined or damage were investigated, the reasons of occurring defects such as gas porosities and ill bonding in the repaired zone were analyzed. And flawless samples were obtained through optimizing laser process parameters and introducing the ultrasonic vibration into laser deposition repair system. The microstructure characteristic of laser deposition repair component and distribution of main alloy elements were investigated, and the microhardness of the laser deposition layer was tested. The results indicate that there is a dense metallurgical bond between the repaired zone and the substrate with the optimized process parameters. While the gas porosities ratio of the laser deposition layer is decrease obviously through introducing the ultrasonic vibration to the repaired system. The component elements are unifomly distributed without fluctuation and segregation in the whole repaired sample. Distribution of microhardness from the substrate to the repaired zone showes an increasing trend.