The invention discloses a carp brain stereotaxic localization assisting device and a localization method, and belongs to the field of brain stereotaxic localization. The invention aims at solving a problem of conventional stereotaxic apparatuses which is inaccurate in localization due to a certain angle difference kept between a three-dimensional coordinate system which is adopted by the conventional stereotaxic apparatuses and the skull surface of a carp. The device is composed of a fixed platform, fish body fixing blocks, gill rods, a sliding rod, sliding rod rails, a box body, sliding blockrails, a rollers and the like; the device, when used, is arranged on a stereotaxic apparatus base; an anesthetized carp is placed on the fixed platform of the device; and the fixed platform is inclined, so that the skull surface of the carp is parallel to the stereotaxic apparatus base for conducting operations. The device provided by the invention has the beneficial effects that instead of converting carp brain tissue magnetic resonance scanning coordinates into coordinates of a stereotaxic apparatus, it can directly conduct operations on the basis of the carp brain tissue magnetic resonancecoordinates; therefore, the device is accurate in localization and simple and convenient to operate. The device provided by the invention is mainly applicable to brain stereotaxic localization of carps, and the device is also suitable for brain stereotaxic localization of other varieties of fishes which are similar with the carps in skull structure.