The High Energy cosmic-Radiation Detection facility (HERD)
is a calorimetry-based cosmic-ray detection mission on board China
space station. A side-on transition radiation detector (TRD) focuses
on the TeV energy range calibration of the HERD calorimeter with an
error of less than 10% by measuring the Lorentz factor γ of
high-energy cosmic-ray protons. A side-on TRD prototype was
developed for the performance study and tested by Deutsches
Elektronen-Synchrotron electron beams. In this paper, the Monte
Carlo simulation based on GEANT4 was compared with the experiment
results. All simulations were in good agreement with the test beam
results.