A multi-position adjustable height seat post comprises an inner tube, an outer tube, a locking assembly, a triggering device, a first extending element, and a second extending element disposed between the tubes. The locking assembly comprises an actuating unit, a plurality of parallel grooves located in the outer tube, a plurality of spherical detent elements located, in the grooves, and a plurality of spherical elements located in the inner tube. The triggering device connects to the actuating unit. The first extending element constantly pushes the to actuating unit moving in a first direction. The second extending element disposes between the tubes. Once the triggering device is triggered, the actuating unit moves in a second direction contrary to the first direction and makes the spherical elements to move inward laterally to let the inner tube and outer tube move relative to each other freely.