The work aims to study the effect of particle size on the pore structure of plasma-splayed Yttria stabilized Zirconia (YSZ) coatings. Thermal barrier coatings were prepared and treated at high temperature thermal cycle by air plasma spraying for YSZ powder in two particle sizes. The difference between pore structures of two coatings and the evolution during thermal cycle were analyzed by quantitative metallography. The thermal cycle life of the coating prepared by 45~60 μm YSZ powder was 40% higher than that of the coating prepared by 15~25 μm particles. The pore structures on two coatings were obviously different. At spraying state, the porosity of coatings prepared by the coarse YSZ particles was higher than that of coatings prepared by the fine particles, while the orientation features of two pores were similar. After thermal cycling, the proportion of the horizontal pores in the coating prepared by the fine particle powder was about 2/3 of the total pores, while in the proportion of the vertical pores on the coatings prepared by coarse particles was higher than that of the horizontal ones. The change of the cumulative pore content with orientation angle was in conformity with the growth law of S-curve. The shape of accumulation curve was similar for the coatings at spraying state. However, the S-curves of the coatings prepared by the two particle sizes after thermal cycling were shifted in two opposite directions. The thermal shock resistance of the coating prepared by YSZ powder in coarse particle size is better than that of coating prepared by the fine particle size powder. The shape of the accumulation change curve for pore content in coatings as the orientation angle can reflect the difference in the pore orientation of the coatings prepared by two different particle sizes.