Abstract: A layer of nickel is coated on the surface of diamond powder by electroless plating. The effects of the plating bath composition and plating conditions on the results of electroless plating of diamond powder are investigated by orthogonal experiments and SEM. The results show that the influence order of complexant on weight gain is as follows: citric acid > ammonia > sodium citrate, and that the weight gain will be reduced without adding sodium citrate. The weight gain rate of electroless plating is related to the nickel grain size deposited on the surface of diamond powder, and the coated diamond powder with less leakage and less continuous crystals can be obtained when pH value is about 4. Nickel slag will be formed when not adding stabilizer, and excessive addition of stabilizer will inhibit the reaction. The reaction will proceed normally if the amount of dispersant is increased at excessive stabilizer. With the increase of diamond addition, the weight gain rate decreases and the best coating would be achieved at diamond addition of 6 g. With the increase of temperature, the rate of weight gain increases and 80~85 ℃ is the optimum range.