Objective To explore the technique and outcome of procedure of B-PT-B, semitendinosus / gracili tendons for combined reconstruction of anterior cruciate ligament ( ACL) and posterior cruate ligament ( PCL) . Method Sixteen diagnosed patients of ACL and PCL were enrolled,including 6 MCL patients,4 PLC patients,and 10 meniscus patients . Patients were reconstructed of combined ACL and PCL under arthroscopy 2 - 6 weeks after injury. 1 /3 of Autogenous B-PT-B was performed only for ACL,hamstring combined autogenous semitendinosus /gracili tendons only for PCL. The interface was fixed with absorbable crushing screw and crossing nail. Results All patients were followed up for a mean of 13 - 28 months( averaging 23 months) . According to the Lysholm rating systems,the scores were 0 - 27( average 8. 9) preoperatively,and improved to 78 - 91 ( average 86. 1 ) postoperatively. Based on the International Knee Documentation Committee( IKDC) evaluation,16 patients were classified as abnormal ( grade C) before operation,while after operation,14 patients were classified as normal ( grade A ) ,2 as close to normal ( grade B ) . Conclusion Combined reconstruction of ACL and PCL with autogenous tendons under arthroscopy can recover stabilization and function of knee.