The invention discloses an automatic control device of a photovoltaic power generation solar panel and a method thereof. In the device, the solar panel is placed on a support base plate hinged to a toothed bar, and a motor drives the toothed bar to move up and down so as to control expansion and retraction of the solar panel. Compared to the prior art, by using the device and the method of the invention, the solar panel is expanded when there is light and generates power, and is automatically retracted when there is no light or weather is bad. A service life of the photovoltaic solar panel is prolonged, the structure is simple, cost is low and popularization is easy to perform.