The effect of particle size distribution of disperse dyes on polyester dyeing was investigated using press cakes of C. I. Disperse Orange 30 and C. I. Disperse Blue 60. The particle size of the dyes which were grinded by milling machine was separated into 0.1~1${mu}{ extrm}{m}$, 1~10${mu}{ extrm}{m}$ and 5~20 ${mu}{ extrm}{m}$ of particle size ranges using a centrifuge. Dyeing poperties such as dyeing rate, exhaustion, solubility and compatibility were estimated according to the particle size distribution of the dyes. Dyes having larger particle size showed lower dyeing rate and exhaustion value in polyester dyeing. Solubility and compatibility were also affected by the particle size distribution of dyes.