Abstract: Sixty wheat cultivars were selected as the experimental materials, and Polyphenol oxidase (PPO) was extracted by citric acid-phosphate buffer from their whole wheat flour. NaDiCa and CuCl2 as PPO inhibitors and activating agent were put into the crude enzymical extract, then PPO activity was determined using spectrophotometer, the results showed that: NaDiCa and CuCl2 can respectively inhibit and active wheat PPO, 0.1mM agents have good inhibition and activation; Environment has no effect on the inhibition and activation, but the wheat genotype and the agents concentration have significant effects; it presents logarithmic relation between wheat PPO activity and concentration of NaDiCa and CuCl2.