In this paper, the flow field in the contraction section of precision water flume was numerically simulated by solving RANS equations. Three different contraction curves were selected for two different contraction sections with different outlet sizes and different contraction ratios. The three contraction curves were judged by three criteria: the flow was separated or not; the adverse pressure gradient changed moderately or not; the flow velocity distribution uniformity. The research shows that the bicubic contraction curve is the best for the contraction section with the outlet size of 250 mm×20 mm; for the contraction section with the export size of 250 mm×10 mm, the Витощинский’s contraction curve is the best. This work can be used as reference for designing the contraction section with optimization.