The construction of relevant standards for building carbon emission assessment in China has just started, and the quantitative analysis method and evaluation system are still imperfect, which hinders the development of lowcarbon building design. Therefore, the use of intelligent energy management system is very necessary. The purpose of this paper is to explore the design optimization of low-carbon buildings based on intelligent energy management systems. Based on the proposed quantitative method of building carbon emission, this paper establishes the quota theoretical system of building carbon emission analysis, and develops the quota based carbon emission calculation software. Smart energy management system is a low-carbon energy-saving system based on the reference of largescale building energy-saving system and combined with energy consumption. It provides a fast and effective calculation tool for the quantitative evaluation of carbon emission of construction projects, so as to realize the carbon emission control and optimization in the early stage of architectural design and construction. On this basis, the evaluation, analysis and calculation method of building structure based on carbon reduction target is proposed, combined with the carbon emission quota management standard proposed in this paper. Taking small high-rise residential buildings as an example, this paper compares and analyzes different building structural systems from the perspectives of structural performance, economy and carbon emission level. It provides a reference for the design and evaluation of low-carbon building structures. The smart energy management system collects user energy use parameters. It uses time period and time sequence to obtain a large amount of data for analysis and integration, which provides users with intuitive energy consumption data. Compared with the traditional architectural design method, the industrialized construction method can save 589.22 megajoules (MJ) per square meter. Based on 29270 megajoules (MJ) per ton of standard coal, the construction area of the case is about 8000 m 2 , and the energy saving of residential buildings is 161.04 tons of standard coal. This research is of great significance in reducing the carbon emission intensity of buildings.