A single peak in thermal desorption profiles of hydrogen, which are measured in low-temperature thermal desorption spectrometry (L-TDS) for a very thin plate specimen of tempered martensitic steel, was reproduced successfully to evaluate the peak temperature by the superposition of two Gaussian distributions. We calculated the parameters concerning the detrapping rate constants for both peaks, which are the trap energy and pre-exponential factor, from the Choo-Lee plot. We confirmed that the Kissinger model incorporating the obtained parameters could simulate the two peaks. In addition, the single peak was also well reproduced by the reaction-diffusion equation based on the McNabb-Foster model incorporating the obtained parameters. From the trapping energy and the trap site concentration which were used for reproducing the single peak, we interpreted that one peak corresponded to dislocation and the other was to grain-boundary.