The invention discloses a double-layer composite tube and a manufacturing method thereof. The double-layer composite tube and the manufacturing method aim to solve the technical problems that black pigment is added into traditional HDPE tubes, accordingly inner walls are not smooth, water scale is prone to being generated, bacteria grow, and secondary pollution of water is caused. The double-layer composite tube comprises an inner layer and an outer layer, the inner layer is made of ultrahigh molecular weight polyethylene and ethylene-vinyl alcohol copolymers or low-density polyethylene, and the outer layer is made of high-density polyethylene, ethylene-vinyl alcohol copolymers and special melanin particles C of PE. The method includes the following steps of material proportioning and dehumidifying, material plastifying, material forming, vacuum sizing and spraying and cooling. The double-layer composite tube has the advantages of being good in toughness and flexibility, high in chemical stability, good in corrosion resistance, good in sealing performance, large in distribution power, long in service life, high in low temperature resistance, hygienic, free of toxin and the like. The manufacturing method is simple, easy to operate and capable of achieving integral production of the double-layer composite tube.