Abstract: We select the seedling healthy rapes and the rapes with different levels of plasmodiophora brassicae growing in the field as the object, explore the effect of rape plasmodiophora brassicae on photosynthesis and enzymatic activity of rape by determining photosynthesis parameters and activity of SOD, POD, CAT in roots and leaves. The results show that, with the increasing of morbidity level, Pn gradually decreases, the highest is 53.08 μmol/m2·s of healthy rapes and the lowest is 23.73 滋mol/m2窑s of rapes in seven levers of plasmodiophora brassicae. SOD activity in roots and leaves decreases firstly and then increases, POD activity decreases firstly then increases and decreases at last. CAT activity in rapes with plasmodiophora brassicae is higher than in healthy rapes.