Various surgical techniques has been advocated for reconstruction of anterior cruciate ligament using the bone-patella tendon-bone graft. Recently endoscopic technique provides good clinical results, with minimal skin incision, accurate positioning of the graft to the femoral tunnel, and decreasing wear rate of the graft. But the graft-tunnel mismatch remains problematic in endoscopic technique. The purpose of this paper is to described causes of the graft-tunnel mismatch and to provide important steps to prevent or minimize the graft-runnel mismatch following anterior cruciate ligament while using the endoscopic technique. Our guideline for prevention of the graft-tunnel mismatch are as follows: (1) The tunnel should he positioned closely to isometric point as much as possible. (2) Anterior placement of the tunnel should be avoided. (3) The change of graft length should be within 2mm between flexion and extension position.