The utility model discloses a brain stereotaxic apparatus sample feeding device which is composed of a support stand, an operating arm installed on the support stand, a microinjector and a fixed supporting frame for fixing the microinjector, wherein the upper end of the fixed supporting frame is fixed on the front edge of the operating arm, the lower end is fixed with the microinjector, the middle portion of the fixed supporting frame is fixed with a connecting block, a screw through hole is arranged on the connecting block, a screw thread boosting bar with a hollow bottom is meshed in the screw through hole, the screw thread boosting bar is vertical to the horizontal surface, and a pushing bar of the microinjector extends into a hollow cavity at the bottom of the screw thread boosting bar and is fixed with the hollow cavity at the bottom of the screw thread boosting bar. The brain stereotaxic apparatus sample feeding device has simple structure and can realize control of trace amount feeding quantity and sampling quantity of liquid.