The invention provides a foldable truss with a self-locking function. The foldable truss comprises a main support arm, an auxiliary support rod, a first hinge, a second hinge, a third hinge, a first support seat and a second support seat. The main support arm is of a quadrangular frame structure. One edge of the frame structure is connected with the first support seat through the first hinge, and an opposite edge is connected with the auxiliary support rod through the second hinge. The main support arm rotates through the first hinge. One end of the auxiliary support rod is connected with the second support seat through the third hinge, and the other end is connected with the main support arm through the second hinge. Two ends of the auxiliary support rod rotate respectively through the second hinge and the third hinge. The foldable truss has the advantages that the structure is simple, folding in a space large in receiving ratio can be realized without additional power, repeated folding and unfolding are available, the folding is in place and reliable, the certain structure rigidity is achieved, the requirements of a tracking antenna are met, and the foldable truss is wide in applicability and popularization value.