Abstract: In this study, leveraging historical power generation data and environmental data, a meticulous selection of clear-sky weather samples was conducted. Employing the solar irradiation model, horizontal irradiance was converted into the inclined irradiance under various combinations of azimuth and tilt angles. Subsequent to this, the ideal current curve of the PV string was calculated.According to the difference characteristics of the peak value of the string current output curve at different angles, the peaks between the ideal and actual current output curves were matched. Based on multiple matching outcomes, a comprehensive assessment of the PV string’s tilt angle and azimuth was effectively achieved. Building upon the foundation of the dual-diode solar cell model, specific angle data encompassing both tilt and azimuth were introduced as pivotal inputs, thereby establishing a PV string fusion model for mountainous power plants. Rigorously validated through experimental verification, this model can accurately simulate the output characteristic curves of PV strings of mountainous power plants online, thus further demonstrating its significant practical utility.