Abstract: Abstract：The physicochemical properties and antioxidant activity of different partical size of broccoli powder made by freeze drying were studied in this paper. The result showed that: the smaller the distribution of granule diameter, the lower the flowability and density, but the higher the dissolvability. The content of Vc and chlorophyll from submicron powder and micro powder had no significant difference, but content of soluble protein of submicron powder was significantly higher than other powder. EC50 of DPPH· were 80～160 mesh: 1.40mg/mL; 160～240 mesh：1.32 mg/mL; 240～500 mesh：1.28 mg/mL;＞500 mesh：1.20 mg/mL, respectively, amount to 2.54×10-3 mg/mL of Vc(positive control). The DPPH·scavenging activity of broccoli powder were strengthened with the decrease of partical size.