An improved gamma-Re-theta t model has been developed to predict the heat transfer of hypersonic boundary layer transition in this paper. A new correlation of momentum thickness Reynolds number for hypersonic boundary layer flow is first presented using local flow variables. In the correlation, the Mach number and Reynolds number are introduced to reflect the compressible effect of hypersonic flow. The function F-onset1 used to control the transition onset as well as several relevant model parameters are also modified to make the gamma-Re-theta t model suitable for hypersonic flow. Two test cases including the hypersonic flow over a flat plate and the X-51A forebody with different Reynolds numbers and wind tunnel noise levels are employed to assess the performance of the improved gamma-Re-theta t model. Compared with the original model and various experiments, the improved gamma-Re-theta t model can successfully predict the changes of Stanton number and heat transfer rate caused by the boundary layer transition. The model can also reasonably reflect the effects of freestream Reynolds number and wind tunnel noise level on hypersonic boundary layer transition. By analyzing the distributions of heat transfer rate on the X-51A forebody, the windward side transition is found to be related to the separation in the compression corner and large separation can cause earlier transition onset in boundary layer. (C) 2016 Elsevier Ltd. All rights reserved.