Establishing monitoring mechanism for water resources carrying capacity is a crucial approach of ensuring regional water security. Since water resources carrying capacity is affected by many complex factors, we built a multiplexed system simulation model based on system dynamics involving economy subsystem, water resources subsystem, water environment subsystem, and society subsystem for Guangdong Province as a case study. On the basis of consistency check, we analyzed the trends of water resources under five scenarios: zero parameter scenario, water-saving scenario, optimized industrial structure scenario, environmental protection scenario, and comprehensive scenario. Results suggest that under zero parameter scenario, water resources carrying capacity was relatively stable; while under water-saving scenario, optimized industrial structure scenario, and environmental protection scenario, the regional economy, water consumption, available water resources and ecological environment was improved in a partial scale; only in comprehensive scenario, all the evaluation indices of water resources carrying capacity can be coordinately optimized. The research provides support for the decision-making in the construction of water-saving society.