The invention discloses a submarine cable protection tube, and the tube comprises a chain-shaped structure which is formed by the holding-on of at least two submarine cable protection tube modules, wherein each submarine cable protection tube module consists of two symmetric monomer structure units which cooperate with each other and are in fastening connection through a steel belt. Each monomer structure unit comprises a head part, a main body and a tail part, wherein the head part is provided with an external groove, and the tail part is provided with an internal convex ring. The external groove and the internal convex ring are in adaptive connection, and the interior of the main body is provided with a central hole. One edge of a side surface of each monomer structure unit is provided with a plurality of projections at intervals, and a plurality of grooves are disposed at the positions, symmetric with the projections, of the other edge of the side surface of each monomer structure unit. The tube employs the module structure units, and can freely change the overall length according to the needs. The design of a convex and concave groove embedding structure on the side surfaces of the units enables the symmetric units not to be shifted in a staggered manner, and enables the tube to wrap a submarine cable more tightly. The tube employs a semi-opened unit structure, employs the steel belt for fastening, and can achieve quick installation.