In order to obtain stable and homogeneous diamond-Ni-P composite electroless plating, dispersants were selected by determining the height of emulsion in the colorimetric cylinder after standing different time.The structure,elemental contents and properties of the diamond-Ni-P composite electroless plating coating were investigated by SEM and EDS. Experimental results show that OP-10 of 50mL•L-1 and softex kw of 1g•L-1 have better dispersing effect to diamond powder of 1g•L-1 in water. This composite electroless plating solution can keep stable for more than twelve or eight hours respectively at 85°C. While in the electroless plating solution, Softex kw of 1g•L-1 has better dispersing effect and can be stable for more than two hours at 85°C. The diamond powder grains in the composite coating are homogeneous and the content of carbon is 2.261 wt% under the certain amount of the selected dispersant. When the content of diamond was 5g•L-1 in the solution, the diamond powders were dispersed non-homogeneously in plating and cluster phenomena were appeared. The composite electroless plating coating consists of amorphous Ni-P and diamond powder. Its hardness and porosity are similar to those of the electroless plating Ni-P coating. The wear-resisting is improved greatly,which is 2.6 times of electroless plating Ni-P or 2 times of that after heat treatment at 400°C for one hour.