There are three methods used in the studies of the urban green ecological effects at home and abroad: First, by the support of GIS, the analysis of the relationship between the urban green and urban microclimate was developed in the mesoscale level; Second, taking a city as a unit, the microclimate effects in green land of different features can be surveyed; Third, based on the plant transpiration theory the microclimate effects are surveyed and calculated. The results on studies of natural ecosystem showed that as an open ecosystem, urban green land can affect the environment around green land through the system exchange. The system exchange between the green land and nongreen land are not only controlled by the plant leaf surface index but also influenced by the area, geometric distribution, forestry, growth yield of the green land, and the environment and climate factors around the green land. Though the plant ecological field theory places emphasis on the spatial relationship among plants, especially on the analysis of competition between plants, but its theoretical framework and method of calculation will be important to the study of ecoeffects of urban green land.Six test sample of different spatial structure were selected in Taiyuan city and the temperature and humidity recorded with a meter. The survey data were analyzed by the plant ecological field theory. Some main targets used to appraise urban green land ecoeffects put forward, these targets concerned ecological field intensity, ecological field gradient and domain. Ecological field intensity defined as the difference between the data in green land and the control group. This is defined as the disturbance range that grass land causes toward the environmental temperature and humidity around it. Ecological field gradient means the disparity between two of nearest data. Domain of ecological field expresses the influence extent of the ecological field. The result showed that green land area, forestry and green growingquantity can influence the characteristic to variety agrees on the same or similar condition. When the green land area reached a certain area, the scope of lowering temperature and raising humidity in per unit area became lower with the increases of green area. Comparing with the forestry ecological field, we founded that the effect of raising humidity was better than lowering temperature in turfgrass.