Due to no spaces in the Spent Fuel Pool (SFP), there is still fuel in the core of Chinshan Nuclear Power Plant (NPP). This study evaluates the Emergency Planning Zone (EPZ) for the Chinshan NPP during the pre-defueled stage of the decommissioning phase and uses the MELCOR Accident Consequence Code System (MACCS) to assess Level 3 early-phase radiological risk. In this work, the evacuation is not considered and extremely conservative meteorological conditions (i.e., a fixed northerly wind at 0.1 m/s, stability class G and no rainfall) are assumed. The results show that under the Design Basis Accident (DBA) cases, the individual effective dose at 0.5 km from the midpoint between the two reactor units is below 50 mSv (regulatory criterion in Taiwan). Under the Severe Accident (SA) case, the annual exceedance probabilities of 50 mSv and 2 Sv at 0.5 km from the midpoint are both below the regulatory criteria of 3.0 × 10⁻⁵ and 3.0 × 10⁻⁶ (regulatory criterion in Taiwan), respectively. In brief, the DBA and SA results indicate that all the EPZ criteria can be satisfied within 0.5 km from the midpoint between the two reactor units under the conservative assumptions adopted in this study and the current 8-km EPZ provides sufficient conservatism in Taiwan. The findings of this study can serve as technical references for EPZ review under similar decommissioning conditions.