Abstract: Basic principles of thermal insulation in sunlight greenhouses was introduced, and was applid in construction and renovation design of flue-cured tobacco seedling cultivation greenhouse．Warming effect of sunlight greenhouses is determined by heating characteristics and insulation performance of shed body．Three methods were mainly used to measure warming effect: sunlight greenhouses insulation ratio, thermal conductivity ratio and perimeter-to-area ratio．Results showed that enlarging sunlight greenhouses area or reducing aspect ratio could increase insulation ratio and reduce thermal conductivity ratio by reducing membrane area．While improving insulation performance of sunlight greenhouses, heating characteristics and effectiveness were improved．Sunlight greenhouses height in three methods on warming effect was different．Based on analysis of three methods applied respectively, considering changes of area, height, and aspect ratio on thermal capacity and light intensity of sunlight greenhouses space, as well as sunlight exposure made membrane produces thermal insulation and other factors．It could provide a relatively complete explanation of changes in heating characteristics, insulation performance, and heating effect of sunlight greenhousess under different areas, heights, and aspect ratios, to serve as a theoretical basis for improving warming effect of flue-cured tobacco seedling cultivation greenhouse．