The utility model relates to a hydraulic active hermetic core taking tool used for oil and gas drilling. An upper connector (1), a bearing base (4), an outer cylinder (13), an outer cylinder short circuit (15) and a core taking driller (16) are orderly threaded to each other. An inner cylinder (14) is disposed in the outer cylinder (13) with the lower end thereof threaded to a core grasper and the upper end thereof connected with a switching connector (12). A spring (10) is arranged in the hollow cavity formed by the inner surface of a spring sleeve (11), a baffle ring (9) and the outer surface of the switching connector (12). The upper end of a spring sleeve (11) is connected with a branch connector (6). The bearing base (4) is provided with an inner step at the step position of the branch connector (6). A bearing (5) is arranged in the hollow cavity formed by the bearing base (4), the branch connector (6) and a baffle block (3). The branch connector (6) is of a hollow structure, with the front and back ends forming a lug and the middle part being a long and thin tube. The utility model has compact structure and can efficiently promote the core grasping reliability of the grasper.