The splitting of particles precipitating from solid solutions, e.g. Ni-based alloy, is studied with the phase field method. The simulation results show that in the single particle system, the nucleuses of crystal with the sizes of 80l to 90l (l= 12.18 Å) split during ageing. The splitting is the result of the interaction between elastic energy and interface energy. During the earlier stage of ageing, the sharpening along of the interface of the initial spheric shape particle will lead to the solute beneficiation at the corner but impoverishment in the center of the particle, it is the splitting incubation stage (SIS). The total interface energy (TIE) appears as being of horizontal step during SIS. The particles split at 300τ (τ=4.65 s) after the SIS and at the end of splitting the TIEs reach their maxima and the total elasic energy (TEE) reaches minimum at 1000τ. The horizontal step during SIS and the extreme points of TIE and TEE are the representative features of splitting. The TIE has SIS but no extreme point lying on TIE and TEE when the particle sizes are bigger than 90l. For the particles with sizes smaller than 80l, the TIE increases up monotonically.