The invention discloses a sealing device for a sea pipe leak stopping pipe clamp and a sea pipe leak stopper. The sealing device comprises two groups of axial sealing assemblies, two groups of radialsealing assemblies, two pistons and driving mechanisms, wherein the two groups of axial sealing assemblies are arranged at the opposite two sides of a plugging region of the sea pipe leak stopping pipe clamp and extend axially, the two groups of radial sealing assemblies are correspondingly arranged at the opposite two ends of the plugging region, the two pistons are arranged at the opposite two ends of the plugging region, and the driving mechanisms are connected with the two pistons; the radial sealing assemblies are correspondingly located between the end parts of the plugging region and the pistons; and the two pistons are driven by the driving mechanisms to move in opposite directions to extrude the radial sealing assemblies, and the radial sealing assemblies are driven to seal a seapipe in a tight holding manner. The sealing device is high in automation degree, simple to operate, safe and reliable; the installation and maintenance process not only can be operated by a diver, butalso can be operated by a remote operated vehicle (ROV), and thereby, the sealing device not only can be used for sea pipe leak stopping pipe clamps in a shallow sea area of which the water depth iswithin 300 m but also can be used for sea pipe leak stopping pipe clamps in a deep sea area of which the water depth is above 300 m, and the problem that the sea pipe leak stopping pipe clamps in thedeep sea area cannot realize rapid and effective sealing is effectively solved.