In the North China Plain,the average annual precipitation is 500-600 mm,74% of which is concentrated in the rainy season.triggering soil leaching and desalinization.When the precipitation exceeds 300 mm in July and August,soil desalinization will be observed,and when a rainfall is over 25 mm,the effect of desalinization in root zone soil will be seen.The key to enhancing the effect of rainfall on salt leaching and desalinization lies in setting up drainage and water management systems、Beginning from 1964,main drainage rivers had been excavated and dredged in the Haihe River Plain year by year,and in 1975 all the five rivets systems of the Haihe River got their own drainage outlets to drain flood.exces"ive rainwater and saline groundwater.Along with the water drainage a lot of salt is drained into the sea.The end of the 1960s the beginning of large-scale exploitation and utilization of groundwater for irrigation.The practice of well irrigation lowers the groundwater table,thus functioning as drainage,reducing phreatic evaporation,increasing rainfall ifiltration and consequently enhancing the effect of rainfall on salt leaching and desalinization.And the practice of replenishing the groundwater with river water Freshens the groundwater.As a resalt,soil secondary salinization has been controlled,and large areas of saline-alkali land ameliorated in the North China Plain.