Abstract: Conservation tillage, which can adapt to agricultural development of northern China well, is a new farming system, and through subsoiling, itcan eliminate the soil compaction created by many years of no-till. Nowadays inthe research field of subsoil technique, Chinese researchers have not conductedthe profound researches on subsoiling effect and economic benefits under conservation tillage, what is more, they have not attached importance to the problems,such as doing harm to maize seedlings, increasing power consumption and reducing economic benefits, etc, which appear frequently during the process of subsoiling for maize. Based on the conservation tillage demonstration sites in northernChina, the authors used more than ten years time and conducted a compositive experimental study of subsoiling effect under conservation tillage since 1993. Thecompositive experiment of subsoiling effect with three different tillage modesof traditional tillage, subsoiling with coverage and no-till with coverage mensurated the data of soil bulk density, water contentt, water use efficiency and yield under different tillage modes, confirmed subsoiling time interval under conservation tillage, i.e., the tillage mode of four-year no-till with coverage plus one-year subsoiling, and the authors analyzed corresponding economic benefits of different tillage modes.The experimental results show, under the condition of conservation tillage, subsoiling every four years can solve soil compaction, keep high water use efficiency and yields of crops continuously and there is no need of subsoiling everyyear. The tillage mode of four-year no-till with coverage plus one-yearsubsoiling is capable of enhancing about 25% economic benefit compared to subsoilingwith coverage(subsoiling every year). At the same time, according to the problems appeared in the process of maize subsoiling, a combined operation scheme of seeding and subsoiling for no-till maize is presented and the experimental result indicates this scheme can account for a serial of above problems existed in the process of maize subsoiling, promote the growth of maize, and increase theyield of maize. It is recommended that the combined operation technique of seeding and subsoiling for no-till maize should be extended in maize-producing areas of northern China.