The invention provides an electric multistage actuating cylinder retracting and releasing locking device which comprises an outer cylinder, a middle cylinder, an inner cylinder, a screw and a two-stage
steel ball lock mechanism mounted on the outer side of the screw. The outer cylinder, the middle cylinder and the inner cylinder are three coaxial sleeves which are sequentially embedded mutually, the middle cylinder and the inner cylinder are fixedly connected with the two-stage
steel ball lock mechanism respectively, and the
steel ball locking mechanism drives
relative motion of upper and lower locking sliders and upper and lower sliding sleeve through
joint action of the screw and upper and lower elastic elements so as to realize locking and unlocking of upper and lower steel balls; a steel ball lock is a mechanical lock, so that the device can bear high
impact load in a locked state; an internal thread of the lower sliding sleeve does not be meshed with an external thread of the screw when a multistage actuating cylinder is at a fully-retracted position, and after the middle cylinder and the inner cylinder complete locking through an upper-stage steel ball lock mechanism, the inner cylinder drives the lower sliding sleeve to move upwards so as to be meshed with the screw to complete unfolding of the middle cylinder, so that due to this stage-by-stage unfolding mode, the multistage actuating cylinder is long in unfolding
stroke and needless of manual operation in the process of retracting and releasing.