The invention discloses a method for determining the filling capacity of sleeve grouting in the prefabricated concrete structure. The method includes: setting a slurry outlet channel between a sleeveoutlet and a prefabricated-part surface outlet, and setting the grouting material end face on one side close to the prefabricated-part surface in the slurry outlet channel to be an impact detection surface; recording the position of the impact detection surface in the slurry outlet channel before detection, arranging an impact device on the impact detection surface, and performing impact test on the impact detection surface; after impacting, recording the position of the impact detection surface in the slurry outlet channel once again; determining the filling capacity of sleeve grouting according to whether or not the grouting material in the slurry outlet channel and the inner wall of the slurry outlet channel slip under the action of impact force, if the impact detection surface producesobvious displacement, judging sleeve grouting to be not full, or otherwise judging sleeve grouting to be full. The method is simple and ingenious in detection principle, convenient in operation, capable of accurately judging whether sleeve grouting is full or not and quite easy to promote.