The invention discloses a composite beam structure of an unmanned aerial vehicle wing and a manufacturing method thereof. The composite beam structure of the unmanned aerial vehicle wing comprises a beam entity structure composed of edge strip substrates, web substrates, square substrates and an internal packing layer in the beam extending direction, and edge strip reinforcing layers and web reinforcing layers which are wrapped outside the beam entity structure; two parallel web substrates are supported at both sides of two parallel edge strip substrates respectively, the internal packing layer is arranged in an intermediate cavity formed by constructing two edge strip substrates and two web substrates, and the square substrates are located at both ends of the internal packing layer, so that the beam entity structure is formed; the edge strip reinforcing layers are covered on the outside surfaces of the edge strip substrates, the web reinforcing layers are covered on the outside surfaces of the edge strip reinforcing layers and the entity structure, and location holes used to connect to wing ribs are formed in the outside surfaces of the web substrates. The composite beam structure of the unmanned aerial vehicle wing disclosed by the invention has the advantages of simple and reasonable structure and low manufacturing cost, and can meet the anti-bending and anti-torsion requirements of the unmanned aerial vehicle wing with high aspect ratio for beams.