Disclosed in the present invention is a subacromial space expander, used for maintaining and increasing the distance between humeral head and acromion and increasing the distance between greater tuberosity and the acromion at shoulder abduction. The subacromial space expander comprises an inflatable air bag provided among the lower surface of the acromion, the humeral head and the greater tuberosity； the inflatable air bag is provided with a first surface abutting against the lower surface of the acromion and a second surface abutting against the humeral head and the greater tuberosity； the inflatable air bag comprises an air bag body having an inner cavity and a diaphragm provided in the inner cavity for dividing the inner cavity into a plurality of inflatable chambers. The subacromial space expander according to the present invention has the advantages that normal biomechanics of a shoulder joint can be rehabilitated, deformation quantity is less when the expander is extruded by a force, no deformation which is too large to cause discomfort and pain on the shoulder joint by extruding surrounding soft tissues of the shoulder joint is caused, the expander may not fall to other portions of the human body under the action of gravity, no discomfort is caused at the other portions, and the expander is easy to popularize.La présente invention porte sur un extenseur d'espace sous-acromial, utilisé pour maintenir et augmenter la distance entre la tête humérale et l'acromion et augmenter la distance entre une plus grande tubérosité et l'acromion lors de l'abduction de l'épaule. L'extenseur d'espace sous-acromial comprend une poche d'air gonflable disposée entre la surface inférieure de l'acromion, la tête humérale et la plus grande tubérosité ； la poche d'air gonflable est pourvue d'une première surface venant en butée contre la surface inférieure de l'acromion et d'une seconde surface venant en butée contre la tête humérale et la plus grande tubérosité ； la poche d'air gon
