The current research on real estate data is insufficient, resulting in the false judgment from the government to the real estate industry, and thus the negative impact on the social economy development. Analyzing the real estate market data, this paper used the data mining technology for the real estate data, and proposed the monitoring index system based on digestion cycle. The detailed calculation was given taking Shanghai data as an example, and the validity was verified by the results. Finally, the Shanghai GIS decision support system for real estate market based on the theoretical research was introduced, and the functions were analyzed.