Abstract: It is always a major event to ensure national grain security for running a country and bringing peace to people. Based on judgment and analysis of food consumption trend, this paper measured the substitution space about the miscellaneous grains of potatoes\|cereals , animal product\|grain ration, feed forage\|feed grain, reasonably. On this basis, the paper also forecasted the grain demand in 2020. The result indicated that the requirement for rice, wheat in 2020 would reduce 539×104  t and 108×104 t, respectively, compared with that in 2014, owing to the factors: food consumption per capita falling down; consumption of miscellaneous grains of potatoes\|cereals increasing. Increasing the proportion of fodder grass in feed for herbivore could not only obviously improve the trophic structure, but also save 1 100×104 t of maize, 770×104 t bean pulp. On the basis of ensuring grain ration safety absolutely, the grain output could be adjusted to 6.04×108 t in 2020 by importing soybean, maize and miscellaneous grains. 567×104 hm2 of land could be saved to develop silo corn, pasture or even lie fallow. These conclusions could offer important decision\|making basis for agricultural supply\|side reform.

Key words: big food concept, grain security, assurance requirement, way and countermeasure

摘要： 确保国家粮食安全始终是治国安邦的头等大事。立足于居民整体食物消费趋势的判断与分析，分别测算了薯类杂粮对谷物、动物产品对口粮、饲草料对饲料粮的替代空间，并在此基础上对2020年粮食需求做出了预测。分析结果表明，受人均口粮消费下降、薯类杂粮口粮消费增加等因素影响，与2014年相比，2020年我国水稻、小麦需求量将分别减少539万t、108万t；增加饲草料在草食动物的饲喂比重既能明显改善其饲料营养结构，还可节约使用籽粒玉米1 100万t、豆粕770万t；在保障口粮绝对安全的基础上，通过进口大豆、适量玉米及杂粮，2020年我国粮食产量可以调减为6.04亿t，调整出567万hm2播种面积用于发展青贮玉米、牧草或休耕。上述结果可为当前农业供给侧改革提供决策参考。

关键词: 大食物理念, 粮食安全, 保障需求, 途径对策