A detailed calibration procedure was considered using the commercial engine simulation package, GT-Power based on the experimental test results of hydrogen fumigation into a HD diesel engine. Initially an essential reverse-run calculation was applied for exploiting the cylinder trapped conditions in addition to the measured burn rate. Applying two distinct phenomenological models in parallel, allowed combustion modelling of premixed H2/air and diesel pilot injection. Utilising a robust optimiser, calibration factors were swept with aim of minimising the RMS error between experimental and predicted burn rate. The optimised calibration factors showed good capability of predicting the in-cylinder pressure and burn rate. Ultimately, by comparing the optimised calibration factors in different operating points, evaluation of the unique dual-fuel combustion phenomenon was possible.