Abstract: A new kind of Co-based alloy coating powder containing certain amount of nano-Al powder was designed. The ceramic phases in the coating were produced by YAG pulse laser inducing in-situ synthesis.  The microstructure morphology and the forming mechanism of the coating were studied by means of scan electronic microscope，optical micrograph analysis techniques and micro-hardness tester. By the pulse laser inducing in-situ synthesis，the interfaces of the thin coatings are metallurgically combined and  the ceramic particles are well dispersed. The micro-hardness of the Co-based composite alloy coating is promoted from HV87 to HV426. The added nano-Al supplies the interior heatfountain，which compensates for the energy loss  caused by the quick heat transmission of Cu-based alloy. The added nano-Al can fully induce the interior chemical reaction，which improves the composite coating forming easily. Ceramic particles are less than 2.0 μm in diameter and dispersed in the strengthened coating.