Abstract: The lake-terrestrial ecotone of the natural-wetland type is the basic reference type for lake-terrestrial ecotone restoration. As an important part of the lake-terrestrial ecotone of natural-wetland type, the radiation belt toward land delimited from the annual average highest water level toward land to some extent. The complexity and transitivity shared by lake-terrestrial ecotone makes it hard to delimit. In order to study the method of delimiting the range of terrestrial radiation zone in natural lake-terrestrial ecotone, took Taihu Lake, Changtan Reservoir and Xiazhu Lake as examples, based on the understanding of the spatial structure characteristics of lake-terrestrial ecotone, calculated the squared euclidean distance (SED) with the important value of hygrophic herbaceous plant, used the moving split-window technology (MSWT) to delimit the range of the terrestrial radiation zone in the lakeside zone, and analyzed the factors affecting the width. The results showed that the widths of the radiant belt toward land of lake-terrestrial ecotone of natural-wetland type of Taihu Lake, Changtan Reservoir and Xiazhu Lake were 15-19 m, 19-31 m, and 17-21 m, respectively. The correlation analysis and redundancy analysis were used to determine the relationship between width, soil physicochemical properties and plants community diversity. The results showed that this range had no significant correlation with soil nutrient content, and was significantly negatively correlated with slope (P < 0.01), and positively correlated with soil moisture (P < 0.05). This study shows that moving split-window technology can accurately delimit the range of terrestrial radiation zone in natural lake-terrestrial ecotone. Soil moisture content is the most important factor affecting the width of the radiant belt toward land of lake-terrestrial ecotone of natural-wetland type. The slope of the radiation belt toward land affects the soil moisture content, drives the distribution of hygrophic herbaceous plants, and is the indirect factor.