ObjectiveTo study the changes and mechanisms of  blood coagulation in children with Kawasaki disease ( KD) in acute stage.MethodsFortyeight KD children were as case group, according to the examination result of coronary artery  ultrosonography ,12 of 48 patients were in coronary artery lesion group(CAL) and 36 patients were in noncoronary artery lesion group(NCAL), another 30 persons were as health control group. Function of blood coagulation including prothrombin time(PT), thrombin time(TT), activated partial thromboplastin time (APTT) and fibrinogen (FIB) were determined and compared among these groups.  ResultsCompared with patients  in control group, the PT,TT and APTT was shorter in CAL group, and the FIB was higher than those in control group, the difference was  significant (P≤0.01)； the PT and APTT were both shorter in NCAL group（P＜0.01）, and FIB was higher (P=0.01); compared with NCAL group, the PT,TT and APTT was shorter in CAL group（P≤0.01）, and the FIB was higher (P=0.02). ConclusionHypercoagulability exists in KD children in acute stage, and is susceptible to coronary artery disease, which may be related to blood vascular inflammation.