This study investigates the characteristics of the prompt radiation field due to the operation of the proposed Taiwan Photon Source (TPS). Two extreme beam loss cases are considered to bound the possible beam loss scenarios in the tunnel; i.e., all electrons are lost at one point, or they are lost uniformly along the whole electron orbit. Energy spectra and dose distributions of the prompt radiation field for the shielding design of the TPS are studied using analytic estimations and Monte Carlo simulations. The radiation levels of photons and neutrons outside the shielding wall are estimated for various operation modes and beam loss scenarios. The calculated results show that the preliminary shielding design of the TPS is highly practicable to achieve its annual design dose limit of 1 mSv for personnel. Meanwhile, the radiation impact on the environment is also far below the regulatory requirement.