- In this paper, a novel strategy for designing the heterogeneous-tree multiplexer is proposed. We build the multiplexer delay model by curve fitting and then formulate the heterogeneous-tree multiplexer design problem as a special type of optimization problem called mixed-integer nonlinear programming (MINLP). A new design parameter, the switch size in each stage, is introduced to improve the speed of the heterogeneous-tree multiplexer. The proposed strategy can determine the multiplexer architecture and the switch size in each stage simultaneously. Three optimization methods are provided to synthesize the heterogeneous-tree multiplexer according to the design specifications.