Abstract: The soil temperature of the marginal area in the greenhouse of steel frame with no pillar was measured and the boundary points were determined in Spring and Winter in Zhengzhou, Henan Province at warm temperate zone. The results showed that the boundary point was different from each other in different days. The boundary point in the last ten days of November was 105 cm apart from the south edge of the greenhouse, whereas in January it was 270 cm, and in the last ten days of March it was only 45 cm. The boundary point was also different from each other in the different time. In January, the boundary point of 6:00～8:00 was the farthest, that was 285 cm, whereas during 15:00～17:00 it was the nearest, that was 150 cm. The boundary point of marginal area can be used as an index of the optimized design of a greenhouse, and it is helpful for the full utilization of the natural rescources protected by the greenhouse..