A photovoltaic air conditioning system startup method, a controller, and a photovoltaic air conditioning system. The photovoltaic air conditioning system starting method includes: when a photovoltaic device meets a preset power generation condition, controlling a bidirectional converter to enter an operating state; and when the bidirectional converter enters the operating state, controlling a direct current-direct current converter connected to the photovoltaic device to enter an operating state, so that the photovoltaic device provides electric energy to an air-conditioning device by means of the direct current-direct current converter.