Abstract: In recent years, more and more special wheat plants that were significantly different from the varieties used in wheat production were found in the wheat field. The impurity affected wheat field scene and reduced the yield. The peasants had to replace the varieties frequently. This situation increased production cost and also made the varieties extension more difficult. The impurity investigation was conducted in 15 counties of 7 cities in Hebei, model test and production demonstration were also done. The result showed that the relation between impurity popularization, level and the yield was positively correlated. The main mixed wheat types, which caused impurity, were mainly spread by the seeds of farm varieties of hexaploid tricicum. The control techniques were list with the seed purity control as the key.