To increase the grain yield per unit area and to enlarge the planting area are two important measures to keep the sustainable
grain yield increase.Because the competition of graincrops, cashcrops and feed crops for farming landbecomestense unceasingly, the
multicropping is the key way adopted to enlarge the planting area and increase the grainyield.In recent years the multicropping index in China has increased to 155% with an annual rate of 0.8%, and the annual increment of planting area has reached 49000 ha. According to the heat conditions, water resources and
irrigation farmingland there still exists a big potential for the multicropping to be exploited. Through the systematical investigation and analysis it has been proved that the potential multicropping index reach 181% and then the potential increment of grain yield be 75.9 million tons in China. There are two ways to develop multicropping in the arid and semiarid areas in northern China, increasing irrigation land and extending film mulching technique.