Urban low carbon development is a huge, complex but open theory and practical system, thus; a research framework and theoretical system from the perspective of system theory is established. Low carbon urban, as a whole system，can be studied from three dimensions of space, time and function. Economic and social natural resources and energy are the input of urban systems as well as environment and emissions is the output. The research of theoretical system of low-carbon urban development in the future should be rich in the following aspects: such as: the structural system and functional characteristics, space system, locality and globalize, city's comprehensive model system of carbon cycle, carbon metabolism process of double impact between nature and man-made, urban carbon emissions and control at different spatial scales, the past, present and future carbon emission inventories and emission reduction path analysis, practical carbon management measures, as well as the methodology of low-carbon urban development and technical support system.