The constitutive model is still not available for theoretical and engineering analysis of HNi55-7-4-2 alloy, which is a new type of wear-resistant brass alloy widely applied to car synchronizer rings and ship condenser tubes etc. In the current investigation, a friction-corrected stress-strain curve was obtained through a hot-compression test to develop the high-temperature constitutive model of HNi55-7-4-2 alloy based on the Hansel–Spittel model. By comparing predicted flow stress and a simulated force-stroke curve with experimental results, the proposed constitutive model was verified. The developed constitutive model was applied to numerically simulate the hot precision forging of a synchronizer ring. The simulation results based on two process plans on material flow and forging defects were validated by process experiment. The Hansel–Spittel high-temperature constitutive model proposed in this work enables the theoretical and engineering analysis of HNi55-7-4-2 alloy.