The invention relates to a system for autonomously tracking sunlight and a control method thereof. The system is composed of a light-operated valve, a photovoltaic panel, and at least three standing posts arranged below the photovoltaic panel; and the upper ends of the standing posts and the lower surface of the photovoltaic panel are in ball connection. The three standing posts include a first standing post, a second standing post, and a third standing post; the lower end of the third standing post is fixedly connected with a substrate; the lower ends of the first standing post and the second standing post are in ball connection with the substrate; and the first standing post, the second standing post, and the third standing post are distributed in a triangular manner. A first hydraulic cylinder and a second hydraulic cylinder are arranged inside the first standing post and the second standing post; the axial lengths of the first standing post and a second adjustable standing post are changed by hydraulic pressure pushing; and vertical reset springs are arranged at the first standing post and the second standing post. The light-operated valve includes a condensation device, wherein the condensation device and the photovoltaic panel are located on the same plane; and the condensation device includes at least one convex lens; and an annular thermal-expansion working-medium valve body is arranged at the lower surface of the condensation device.