The hydrolysis conditions of antioxidant peptides from Spirulina powder using alcalase were optimized by single factor methods and the Box-Behnken experiments, in order to improve the antioxidant abilities and the yield of Spirulina peptides.The results showed that alcalase has the highest hydrolysis ability compared with other commercial proteases, incluing papain, trypsase and flavourzyme, and it's optimum hydrolysis conditions were 55.46℃, pH 6.71 and the solid liquid ratio was 1∶10.83. When the Spirulina powder were hydrolyzed for 240min under the optimized conditions, the yield of the Spirulina peptides was 58.50%, increasing by 15.61% compared with the control. The DPPH radical scavenging ability of Spirulina peptides reached 77.597%, at the mass fraction of Spirulina peptides was 0.86g/L, increased by 7.62% compared with the control.