The change of the maize yield in different regions is mainly caused by the ecological difference. At the same time, higher plant density is an effective measure to increase grain yield. In order to find out the plant densities response on growth and yield of maize in cold region under different ecological conditions, variety and density of interaction were designed in Harbin, Lanxi, Fuyu which are three ecological zones in Heilongjiang Province. The results showed that, ear height and stem perimeter were mainly affected by ecological conditions. Spatial distribution of LAI was significantly affected by regional ecological conditions. The proportion of bottom leaves was the highest in high yield region. The effect of regional ecological conditions on dry matter accumulation after silking was greater than that of density. The effect of regulating density was obvious in Harbin and Lanxi, and the suitable density was 75 000 plant/ha. Improving soil in Fuyu area was the main way to increase yield.