The invention discloses a startup controllable photovoltaic ventilation sun-shading system which is characterized by comprising an enclosed cavity, a ventilator and a curtain wall, wherein the enclosed cavity comprises a photovoltaic module, an inclined plane perforated aluminum panel, an outdoor upper perforated aluminum panel, an indoor upper perforated aluminum panel, a lower perforated aluminum panel, heat preservation cotton and a waterproof board. The curtain wall comprises a fixed casement and an opening casement, an enclosed aluminum panel is arranged on the outer side of the opening casement, the ventilator is mounted on the lower side of the indoor upper perforated aluminum panel and comprises a motor, a transmission device and a baffle plate, the baffle plate can rotate by 180 degrees to adjust airflow directions, a switch of the ventilator can be independently controlled or connected into a building automatic control system for uniform control, and startup modes of summer, transition seasons and winter are adjusted. The power generation efficiency of a solar battery can be improved, solar radiation heat entering an indoor environment is decreased, indoor air quality is improved, building energy consumption is maximally reduced by natural ventilation, and application prospect is quite wide.