Abstract: The effects of seedtime on maize hybrids under natural precipitation were investigated. The results showed ASI were lengthen sowing earlier, and short ASI was benefit for pollination. Generally, planting period between end of April and beginning of May were better for yield. Some hybrids had high yield no matter planting period, such as Jingdan 28, ZX584. Some hybrids were fit for planted at end of April, such as jingke 521, Nongda 95, Nongda86, which has long growth period.