The invention discloses a basin future hydroelectric power generation capacity prediction method and system considering climate change, and belongs to the field of hydrological forecasting and power generation scheduling crossover, and the method comprises the steps: predicting basin future rainfall and air temperature scenes through the combination of GCMs forecasting factors and a statistical downscaling model; collecting historical runoff data, inputting basin historical meteorological data and the historical runoff data into the VIC hydrological model, calibrating and checking model parameters of the VIC hydrological model to obtain a basin rainfall runoff model, and inputting predicted basin future rainfall and temperature scenes into the rainfall runoff model to obtain a basin section future runoff scene; and establishing a basin reservoir group combined power generation optimization scheduling model, inputting the basin section future runoff situation into the basin reservoir group combined power generation optimization scheduling model, and predicting the basin future hydropower generation capacity. Basin climate changes are considered, uneven basin underlying surface distribution is considered, and the problem of dimensionality disasters of large-scale reservoir group scheduling is relieved.