The coarsening behavior of (Ni,Co)2Si particles in Cu-Ni-Co-Si alloy was investigated by experimental observations and coarsening kinetics calculations when aged at 450,500,550 and 600 ℃ for different durations.The results show that the critical particle radius for coherence mismatch is found to be 10.3 nm,and particles larger than 25 nm are generally semi-coherent.The relationship of (Ni,Co)2Si particles size and aging time follows Lifshitz,Slyosov and Wagner (LSW) theory.The particle size distributions fit well to the LSW theoretical distribution.The activation energy for (Ni,Co)2Si coarsening is accurately determined to be (216.21 ± 5.18) kJ·mol-1 when considering the effect of temperature on the solution concentrations in matrix.The coarsening of (Ni,Co)2Si particles in Cu-Ni-Co-Si alloy is controlled by diffusion of Ni,Co and Si in Cu matrix.The growth of particles for long durations suggests that vacancies can be trapped within the structure for long time despite their mobility.