The invention discloses a method detecting activity of plant superoxide dismutase, catalase and peroxidase, which comprises the steps of grinding a sample by using a liquid nitrogen method, extracting three enzymes simultaneously by adopting one buffer solution, detecting enzyme activity and the like. In the method, SOD, CAT and POD in plants can be simultaneously extracted by adopting one buffer solution, so that the method fulfills the aim of simply and quickly detecting the enzyme activity of the SOD, CAT and POD, simplifies operation, saves time and labor, reduces the using amount of samples and reagent and the like, and contributes to the realization of batch operation, and the detection result is similar to that of the conventional method. Furthermore, the sample is ground by adopting a liquid nitrogen grinding method before enzyme solution is extracted, so that the method has the advantages of high grinding speed, good cell crushing effect and high extraction efficiency.