Freshwater, which is the receiving water of Inland Nuclear Power Plant (INPP), has a lower environment capacity and higher sensitivity to radioactivity comparing with the receiving sea water of Coastal Nuclear Power Plant (CNPP). Focus on the radionuclides in freshwater under INPP normal operating condition, this paper proposed four source items: direct liquid release item, wet deposition item, dry deposition item, and the second run-off item, and also developed their calculation models. These models were then applied to Xianning INPP and its receiving water Fushui reservoir in China. The downstream 1km and the dam were set as sensitive points to simulate the concentration of 137Cs and other effluent radionuclides. Results showed that the direct liquid release item was the main source item under INPP normal operation, 137Cs had a good representative for the variation of total radionuclides concentration with downstream distance. 137Cs concentration at downstream 1km, at the dam, were 1.89 × 101 Bq m−3, 8.04 Bq m−3, respectively; the total radioactive concentration at 1km, at the dam, were 1.65 × 102 Bq m−3, 4.73 × 101 Bq m−3, respectively. Compared with the current two radioactivity limits in freshwater: GB 18871 Food general action level-137Cs, and 1 km downstream total β concentration, the radioactive concentrations under INPP normal operation in this case were all acceptable.