This dataset represents the average power generation situation of medium reservoir-dam type hydropower stations (installed capacity ≥50, <300 MW) in the Zhejiang region of China. A reservoir-dam type hydropower station has 1 reservoir to play a regulating and storage role. The greenhouse gas (mainly for CO2 and CH4) emissions over the reservoir life cycle are estimated based on the Tier 1 method of the National Greenhouse Gas Inventory Guidelines (2019 revision), and the emission factors are adjusted according to the local climate zone and the reservoir age. The hydropower station parameters are set according to design specification standards, namely the technical service life of small hydropower projects is 30 years, that of medium hydropower projects is 50 years, and that of medium hydropower projects is 100 years. The key data are mainly sourced from official statistics and public reports.