In order to improve the radiation-hardened ability of the InP HEMT by optimizing the epitaxial structure design, a series of InP HEMT epitaxial structure materials with different structure parameters were grown by gas source molecular beam epitaxy (GSMBE). These samples are irradiated at room temperature by 1.5 MeV electron beam at the same irradiation fluence of 2?1015cm-2. The electrical properties of the two-dimensional electron gas (2DEG) for InP HEMT epitaxial materials before and after irradiation are measured by hall measurements to obtain the changes of the normalized 2DEG density and electron mobility along with the epitaxial structure parameters. The relationship between 2DEG radiation damage and epitaxial structure parameters (such as Si-δ-doping density, spacer thickness, channel thickness and channel In content) of InP HEMT epitaxial structure materials was analyzed. The results show that the 2DEG of the InP HEMT epitaxial structure material with higher Si-δ-doping density, thinner spacer thickness, thicker channel thickness and lower channel In content has lower radiation damage, which earned a stronger radiation-hardened ability.