Abstract: The world grain production was increasing rapidly during 1950 to 1984,and the average increasing rate was 2.9 percent per annum during this period;but the increasing rate,however,was remarkably reduced to 0.7 percent per annum during 1984 to 1992.The author holds that the rapid increasing rate for the former period is caused by the progress and application of science and technology to agriculture.According to the statistics it is found that the increasing rate of grain production per capita was more than 30 percent per decade during 1950 to 1980,but the rate tended downwards to negative value after middle 80's.The author considers the main causes for slowing or dropping of world grain production are the globle deterioration of agro-eco-environment and the rapid increasing of world population.Then the author discussed the possible ways for preventing the dropping of world grain production.