Objective To study the forearm angulation deformities and observe its influence on the rotation function of the forearm. The importance of the interosseous to forearm rotation function was also ana-lyzed. Methods Eight human cadaver specimens, with the forearm superfical and deep fascia， ante-branchial extensor and flexor groups dissected off were used to study the origin and insertion of the pronator teres and supinator, and the movements of the fibers of the interosseous membrane and oblique cord during forearm rotation. Single and double fracutures of the radius and the ulna were produced in ten other human cadaver upper limb specimens with the pronator teres, supinator, interosseous membrane， oblique cord, proximal and distal radio-ulnar joint preserved. The fractures were fixed with plates and screws, and were made into models with different directions and degrees of angulation deformity. The upper limb were fixed with elbow at 90° of flexion in order to observe the effects of angulation deformities upon the forearm rotation function. Results The oblique cord and the upper third interosseous membrane fibres control the excessive pronation of the forearm while the middle and lower third interosseous membrane fibres control the excessive supination; so the oblique cord and interosseous membrane limited the rotation range of the forearm. The forearm angulate deformity resulted from single or double fractures are both be able to cause the forearm ro-tational disturbance; when the angular deformity exceeds 5°，disturbance of rotational function of the forearm will occur. The disorder of interosseous membrane and the oblique cord, the slope of the articulus radio-ulnaris distalis and proximalis and the osseous obstruction are the main causes of the disturbance of rotation function. Conclusion The interosseous membrane limits the scope of forearm rotation and the deformity of angulation can cause the hindrance of the forearm rotation.