Abstract: The terrain in mountainous areas is undulating and has varying aspects. In conventional photovoltaic design, the entire project adopts a single azimuth angle, tilt angle, and spacing, which leads to problems such as small photovoltaic installed capacity and low power generation. To fully utilize land and improve the rate of return, this paper first uses the total annual irradiation as the main basis for solar radiation analysis and selects land with suitable orientation and slope. Then, by using the regional dynamic variable method, the azimuth angle, tilt angle, and spacing of photovoltaic modules are optimized and adjusted by region to achieve the optimal layout of photovoltaic systems in different areas. Simulation results verify that, in mountainous photovoltaic design, the regional dynamic variable method can make full use of land and significantly improve photovoltaic installed capacity, power generation, and the rate of return.