据预测21世纪中期我国人口将净增2〜3亿，而耕地减少累计量将达1800万hm²,二者叠加到21世纪中叶我国将缺少4〜5亿人口的生存空间，人口、资源、环境形势非常严峻；而如何拓展生存空间的形势也是极其严重的，河流上游封山育林，中游退田还湖，但沿海滩涂却可提供大量后备土地资源。历史上我国退海、围海之地达10余万km²。近50年来，加大围海造地力度，新增了11000〜12000km²土地。本文提出2050年前再造10000〜15000km²生存空间，为2000〜3000万人提供就业机会，还着重提出未来50年围垦难点所在是低滩围垦。根据人海泥沙自然造陆与所需造陆之间的差值，必需以人工促淤和生物促淤工程来弥补自然成陆泥沙之不足。还需在提高环境监测、预测的精度，以及工程技术等方面的技术创新。

It was predicted that the population of China will increase by 2〜3 hundred millions by the middle of next century, but the arable land will decrease by 18 million ha. This means that there will be a shortage of living space for 4〜5 hundred million populations, which will aggravate the situations of population, resources and environment. To expend living space is difficult duo to closing off afforested mountain for protection on upstream and recovering lakes from onec reclaimed farmland. However, the tidal flats along the coasts can provide a large amount of land resources. Historically, there were over 100 000 km² obtained from land progression and reclamation. In recent 50 years, China has acquired 11 000～12 000 km² new land with enhancing reclamation. This paper suggests making 10 000 — 15 000 km² living space for 20～30 millions population to get employment before the year 2050. The reclaimation to lower tidal flats is the key and difficult point in the next 50 years. According to the sediment shortage from sea or river between artificial landmaking and natural landmaking, the artificial impelling siltation and bio-impelling siltation engineerings are necessary to make up for sediment shortage of natural land-making. Besides, it is also necessary to improve environmental monitor and prediction precision and to piake innovations on engineering technology and so on.