Coke powder (CP) added as the substitution of lean coal for coal blending was carried out in 5 kg coke oven. The influences of the particle size, the particle size interval and the amount of CP on the coke quality were investigated. The interfaces in which CP added inset the coke were discussed by means of microplariscope and SEM to confirm the effect of the microstructure on the coke quality. The results showed that the optimal particle size interval, the particle size and the amount of CP were 0.1~0.2 mm, <0.3 mm and 3 wt%, respectively.