The invention discloses a sealing structure for a mechanical tee joint, and belongs to the field of oil and gas pipelines. The sealing structure comprises at least one pair of convex sealing groups, at least one pair of concave sealing groups and at least one pair of axial sealing pieces, wherein the number of convex sealing pieces is the same as the number of concave sealing pieces, and at leastone pair of convex sealing group and at least one pair of concave sealing group and at least one pair of axial sealing piece are in one-to-one correspondence; when in a using state, the pair of convexsealing groups and the pair of concave sealing groups form a pair of annular sealing groups, and are radially and symmetrically distributed on the two sides of the interior of the mechanical tee joint, the two ends of the pair of axial sealing pieces are in sealing connection with the outer sides of the joint positions of the pair of annular sealing groups, and the pair of axial sealing pieces are axially symmetric and are mutually parallel. According to the structure, at least one pair of convex sealing groups, at least one pair of concave sealing groups and at least one pair of axial sealing pieces form at least one three-dimensional space to carry out effective sealing, so that the leakage phenomenon between the inner surface of the mechanical tee joint and the outer surface of the oiland gas pipeline is avoided.