Abstract: The theory of alkali extraction and acid precipitation was employed to optimize the extraction conditions of protein from Metastasis Japonica Makino nutshell ( MJNP) , and protein extraction rate as index, by means of the single factor experiments and orthogonal experiment.The results showed that the optimum conditions were as follows: ratio of solid to liquid of1∶ 20 ( g/m L) , solution p H11.5, temperature of 60 ℃ and extraction time of 1.0 h, and the average extraction yield was 89.18%.Antioxidant experiments were primarily evaluated, under the condition of the optimized process, the protein had the scavenging capacity against DPPH· and ·OH with the scavenging rate of 79.45% ( 8 mg/m L) and 55.35% ( 8 mg/m L) , the IC50 value of DPPH·, and ·OH was 4.19 mg/m L and 3.30 mg/m L, respectively. Moreover, the protein extracted from Metastasis Japonica Makino nutshell possessed weaker reducing power than VC.