Lifting jack

The utility model discloses a lifting jack, which relates to the technical field of pre-stress and comprises an upper support, an upper automatic tool anchor, a jack, a lower support and a lower automatic tool anchor, and a cylinder body of the jack is connected with the bottom end of the upper support and the top end of the lower support; the upper automatic tool anchor is connected with a jack piston, and an upper rotation stopping device is arranged on a base of the upper automatic tool anchor; a guide plate is arranged above the upper bracket; the lower automatic tool anchor is mounted on the lower bracket base; a lower rotation stopping device is arranged at the bottom of the lower bracket base; a guide cylinder is sleeved in the jack, and a displacement sensor assembly and a balance valve are arranged on the outer side of the jack. The lifting jack can solve the problems that an existing lifting jack clamping piece is blocked and unsmooth in anchor withdrawing, the clamping piece is uneven in clamping,