The T800 cobalt-based alloy has excellent high-temperature wear resistance and is widely used for surface strengthening of aero-engine hot-end components. In this paper, benefiting from the advantages of laser direct deposition technology, defect-free T800 cobalt-based alloy wear blocks are successfully prepared on K417G substrate. To investigate the microstructure and properties of the laser direct-deposited T800 cobalt-based alloy wear blocks, microstructure and microhardness analyses are performed on the wear blocks, comparing the results with those of the conventional overlay wear blocks of a part. The experimental results show that the microhardness of laser direct-deposited wear block from the top of the wear to the base material displays a continuous non-linear decreasing trend, and the hardness of heat-affected zone without surfacing welding is higher than that of wear-resistant block. The microhardness of laser direct-deposited wear block is as high as 704 HV, which is much higher than the 340 HV of the surfacing wear block. The thermal influence of laser direct-deposited wear block on the base material is small, and the depth of heat-affected zone is about 180 μm, which is much smaller than the heat-affected zone of the surfacing.