The utility model relates to a special-purpose reactor for an active power filter. The utility model is characterized in that two winding groups is sleeved in parallel on square U type magnetic cores which are buckled correspondingly, and an air clearance filling piece is arranged between the upper magnetic core and the lower magnetic core; two outer frames and two inner frames are threaded into the two winding groups and respectively surrounded on the outer sides and the inner sides of a left pole and a right pole; the inner frames are arranged at the two inner angle of the magnetic core, an outer frame connecting plate is connected with two outer frames, and a filling layer is arranged between the lower part magnetic core and a bottom plate; a bolt sleeve spring cushion is respectively adopted to be threaded into the end part hole of the outer frame from the lower part of the bottom part, the upper magnetic core, the lower magnetic core and the bottom plate are clamped as a whole through a bolt; the outer frame connecting plate connects and fixes the corresponding outer frame. The structure of the utility model is simple, the design is reasonable, the volume is reduced, the process is simplified, the cost is reduce, the performance is stable, safe and reliable, at the same time, the service life of the reactor is enhanced. The operation is convenient, the application is wide, and thus the utility model is suitable for the scale production.