Abstract: Diamond particle content is the key to the performance of diamond composite coating.Selecting different volume fractions of alkyl bromide as the additives, we studied the effect of additive volume fraction on the composite amount of diamond particles and selected the optimum fraction of the addictive.We also studied the influences of current density and diamond particle mass concentration on the amount of diamond particles.The results showed that the composite amount of diamond particles increased first and then decreased with the increase of additive volume fraction with the optimum additive fraction of 0.8mL/L, and that the composite amount of diamond particles increased continuously when controlling the mass concetration of diamond particles in the range of 2.5~40g/L.Current density had an obvious effect on the compound amount of diamond particles, which increasing rapidly and then decreasing slowly with the increase of current density.