The International Workshop on Meta-Synthesis and Complex Systems is a series of workshops to facilitate the exchanges between scholars in the field of systems science and complex problem solving. After successful MCS'2001(Beijing), MCS'2002 (Shanghai, together with KSS'2002), MCS'2003 (Guangzhou, together with KSS'2003), MCS'2004 (Beijing), MCS'2005 (Kobe, one workshop at IFSR'2005), MCS'2006 (Beijing, together with KSS'2006) and MCS'2007 (Beijing, one workshop at ICCS'2007), MCS'2008 (Singapore, a track at IEEE SMC’2008), MCS serial workshops gain so much attention worldwide. MCS’2009 will be continuously held to provide opportunities for those researchers who are interested in systems sciences, complex problem solving and advanced modeling, meta-synthesis, artificial life, knowledge-oriented technology and integration, decision sciences and supporting technologies, etc. with the to facilitate interdisciplinary studies by joining the 20th International Conference on Multi-Criteria Decision Making (MCDM’2009) in Chengdu/ Jiuzhaigou in June of 2009. In consideration of the topics, scopes, paper quality improvement, and increasing participants, especially more concerns from young people, the adoption of MCS as one part of MCDM’2009 will bring new views or new problems about system modeling and complex problem solving especially during the unstructured social problem solving to MCDM. Also MCS workshop will be benefited from much wider community and exchanges. We hope to see a growing community to distribute new ideas and latest research results on effective concepts, methodologies and advanced tools to tackle those wicked problems and explore next-generation tools for complex system modeling and human decision making. Joining MCDM’2009 will help MCS workshop to intensify the research on MCDM practically applied into the meta-synthesis and complex problem solving studies, such as exploring new or implementing available consensus technologies into meta-synthetic system enabled by Web 2.0 technologies.