Objective　To provide clinical anatomy for the way of endoscopic anterior ulnar nerve subcutaneous transposition.　Methods　the length of ulnar nerve free in the forearm and the upper arm,the distance from the first motor branch to the ?exor carpi ulnaris muscle tothe medial epicondyle were measured in ten fresh limbs from fresh cadavers and twenty patients. Simulative surgery were performed on four limbs from cadavers.　Results　In this surgery ,the length of ulnar nerve free in the forearm was（3.90±0.145）cm（3.64~4.23 cm）,free in the upper arm was（4.21±0.18）cm（3.80~4.53 cm）,the first motor branch to the ?exor carpi ulnaris muscle was （2.18±0.38）cm（1.13~2.72 cm）away from the medial humoral epicondyle. In this surgery, the surgical incision was 2 cm longitudinal incision between the medial epicondyle and the olecranon,the forearm axis of the endoscopic operation was about 7 cm line on the line connecting the midpoint between the medial epicondyle and the olecranon to the pisiform,the upper arm axis was about an 8cm line on the line connecting the midpoint on the medial epicondyle and the olecranon to the midpoint on the medial septum of biceps;the suitable and the olecranon regional the endoscopic operation tissue level was the surface of arcuate ligament of Osborne , ?exor carpi ulnaris muscle in the forearm and deep fascia in the upper arm. Simulative surgery was successful.　Conclusion　This study confirmed this surgical approach was feasible, and could achieve the desired results.