Abstract: Considering the tradeoff between conflicting objectives in a water conservancy project in uncertain environment is a difficult task. We present two new piecewise functions, a double exponential function and a quadratic function, to simulate the relationship between the construction quality and limit time of a project, and then develop a fuzzy multi-mode discrete time-cost-quality tradeoff model for water conservancy projects. This model solves a NP-hard problem and adopts a Particle Swarm Optimization algorithm to obtain the optimal solutions. Comparison of the calculations with previous studies verifies the model and its calculation method. A case study of a water conservancy project is given, and the optimization results lay a theoretical basis for project planning and construction scheduling.