Negative-pressure ventilating and lighting method of roof and lighting and ventilating device

The invention discloses a negative-pressure ventilating and lighting method. The method comprises the following steps: (1) the lighting and ventilating device is arranged on a roof; the lighting and ventilating device is provided with a roof hood, and a lighting window which is formed in the lower part of the roof hood; a reflecting metal barrel body is arranged at the lower part of the lighting window; (2) the lighting and ventilating device on the roof is communicated with the inside of a room; (3) indoor air and outdoor air convectively flow through the roof hood; (4) the reflecting metal barrel body is irradiated with sunshine in order to heat to cause upper and lower temperature difference, and hot pressure raising air is realized; and (5) the sunshine irradiates the inside of the room through the lighting window. The invention also discloses the lighting and ventilating device. According to the method and the device, a lighting duct is arranged, and the lighting and ventilating functions are integrated;