用琼脂糖-纤维蛋白平板法对纳豆冻干粉中纳豆激酶活性进行测定，在检测酶浓度单位在2000~10000U/ml时呈现很好的2次曲线关系，蚓激酶浓度单位-两垂直直径的乘积回归方程为y=-0.0000004839 x2+0.02203 x-12.2715，相关系数r2=0.9993。本法回收率范围在89.53%~100.75%，平均回收率为94.7%，RSD为4.2%。“,”The activities of Nat okinase(NK)in nat o freeze-dried powder was assessed by agar-fibrin plate assay,it displays a good quadratic relations under the enzyme concentration of 0.30%~0.40%. The product of the regression equation between concentration of vermis kinase and two vertical diameter was y=-0.0000004839x2+0.02203-12.2715,The cor elation coef icient was 0.9993.The recovery of the method was found to be in the range of 89.53%-100.75%,the average recovery was 94.7%,RSD=4.2%.