Abstract: Heat flux calculation and correction methods of slug calorimeter were studied in order to reduce measurement error of heat flux. Based on the energy conservation principle and the heat transfer theory, the heat transfer model and calculation method of slug calorimeter with insulating sleeve were built. By analyzing the simulation model of slug calorimeter, the method of extracting the temperature rise rate and the main factors affecting the calculation error were given. Finally the direct comparison calibration correction method and the numerical calculation correction method based on heat flux calibration were proposed. The simulation and test results show that the two methods can greatly reduce the heat flux measurement error. The measurement error of the direct comparison calibration correction method is relatively smaller but the method requires that the heat flux calibration system can cover the heat flux measurement range. While the numerical calculation correction method based on heat flux calibration has lower requirement on the heat flux calibration system and thus has a wilder application field.