OBJECTIVE To employ trans-esophageal echocardiography (TEE) to observe the tourniquet's influence on cardiac function in total knee arthroplasty (TKA). METHODS Twenty ASA I-II patients undergoing TKA under general anesthesia from September 2011 to February 2012 at Department of Orthopedics, Beijing Jishuitan Hospital were selected. Tourniquet was loosened at 30 minutes after the start of TKA. And TEE was employed to observe the occurrence rate and degree of intra-cardiac embolus and the changes of cardiac function at 5, 10 and 15 min post-loosening respectively. RESULTS Different degrees of "meteor-shaped" microemboli images appeared in right atriums of all patients. The "meteor shape" image was the most obvious after loosening for 5 min. It started to decrease after 10 min, persisted generally and declined further after 15 min. The left ventricular areas at end diastole (LVAd) after loosening tourniquet for 5, 10 and 15 min were (7.62 ± 0.54), (7.86 ± 0.46) and (8.55 ± 0.56) cm(2) respectively. And there were remarkable changes compared with the area (9.80 ± 0.48) cm(2) pre-loosening (P < 0.01). The fractional area change (FAC) showed obvious decrease since loosening for 5 min (P < 0.01). CONCLUSION Massive meteor-shaped microembolis appear on TEE with weakened cardiac function.