Abstract: Aiming at addressing the critical issues of power supply, heating, oxygen supply, and purified water provision for buildings in alpine and high-altitude areas, this study proposes a distributed energy system based on photovoltaic power generation, taking a typical single-story building in Lhasa, Tibet Autonomous Region, as the research object. Simulation calculations using DeST software determined the building's average heating index to be 51.82 W/m² and the annual electricity demand to be 3 040.4 kWh. A mathematical model of the system was established, incorporating PV generation, air-source heat pumps, a hydrogen-oxygen production system via electrolysis, energy storage systems, and fuel cells. The system's annualized cost, energy self-sufficiency rate, and energy system efficiency were set as optimization objectives. The optimization process involved efficient solving using the CPLEX and IPOTO solvers. The normalized weighted sum method was employed to obtain the Pareto solution set for system capacity configuration. The entropy weight-TOPSIS method was then applied for multi-dimensional evaluation of the solution set, determining the weight distribution among the three objectives as 0.23, 0.29, and 0.48, respectively, thereby obtaining the optimal system capacity configuration. The optimization results show an annualized cost of 8 700 yuan, an energy self-sufficiency rate of 87.59%, and an energy system efficiency of 83.34%. Power balance analysis on typical days verified the system's capability for multi-energy flow coordination across different seasons, demonstrating that the configured system achieves good economic performance and stability while meeting complex load demands, and realizes reliable operation and multi-energy complementarity under extreme environmental conditions. Finally, sensitivity analysis identified the photovoltaic feed-in tariff and the coefficient of performance of the heat pump unit as the primary factors influencing the investment payback period and the energy system efficiency, respectively. This study provides theoretical support for the integrated design and application of distributed energy systems in buildings located in alpine and high-altitude regions.