This study was conducted to evaluate the effects of different particle sizes on feed processing quality and growth performance of broilers at different growth stages. Eight hundred and sixty four one-day-old white feather Arbor Acres (AA) broilers were randomly divided into 6 groups with 8 replicates per group and 18 boilers per replicate. The experiment lasted for 42 days consisting of early period (1 to 21 days of age) and later period (22 to 42 days of age) two periods. The diets of early period and later period were grinded by 1.5, 2.0 and 2.5 mm mesh size of screen, respectively, and 4 replicates were set per mesh size of screen. Three groups were set in early period, twenty four replicates were set in 1.5 mm group, sixteen replicates were set in 2.0 mm group, and eight replicates were set in 2.5 mm group. Six groups were set in later period, 1.5 mm group was divided into 3 equal groups, 2.0 mm group was divided into 2 equal groups, and 2.5 mm group was the same, eight replicates were set per group. The results showed as follows:1) geometric mean particle size of feeds was increased with the increase of mesh size of screen, and geometric mean particle size in 2.5 mm group was significantly higher than that in 1.5 and 2.0 groups (P<0.05). Particle durability index (PDI), particle hardness and starch gelatinization degree were decreased with the increase of mesh size of screen, and PDI and particle hardness in 1.5 mm group were significantly higher than those in 2.0 and 2.5 groups (P<0.05). There was no significant difference in crude protein digestibility in vitro of feeds among all group with the increase of mesh size of screen (P>0.05). 2) Average body weight at 21 days of age, average daily feed intake (ADFI) and average daily gain (ADG) in 2.0 mm group were the highest from 1 to 21 days of age. Average body weight at 42 days of age and ADG in 2.0 mm in early period and 2.5 mm in later period group were the highest and the ratio of feed to gain was the lowest, and ADFI in 1.5 mm in early period and 2.5 mm in later period group was the highest from 22 to 42 days of age. The results show that growth performance in 2.0 mm in early period and 2.5 mm in later period group is the best. Thus, the diets are grinded by 2.0 mm mesh size of screen in early period and 2.5 mm mesh size of screen in later period to get the best growth performance of broilers.