This paper designed and developed a marketing decision support system based on cloud computing, which interacted with other sub-systems, and together made up the entire management decision support system. Designed the distributed database, and the system could both process local database independently and read remote databases. The model base contained various marketing decision models, and complex decision problems could be solved by model combining. The system flow fully considered the human-computer interaction, and user's judgment was included in the decision making process. Completed the system development, and used simulation data to test the system. The running results show that the system is stable, the sub-modules join well, and the MDSS achieves data sharing with other sub-systems.