Abstract: Objective To study the inhibitory effect of arachidonic acid pathway in platelets on clot formation and its correlation with ADP receptor inhibition.Methods Eighty patients with acute coronary syndrome were treated with aspirin（100mg） in combination with clopidogrel（75mg） daily.Inhibitory rate of arachidonic acid pathway and ADP receptor pathway in platelets were detected by thromboelastography.The following varibles of arachidonic acid channel were also recorded:αangle,K time,maximum amplitude（MA） and time to MA（TMA）.Results The inhibitory rate of arachidonic acid pathway and ADP receptor pathway was 81.7%±20.7% and 65.9%±25.3%,respectively.The α angle,MA and TMA were（48.2±15.9）°,（20.8±14.2）mm and（13.8±7.5）min,respectively.The α angle became smaller,the MA decreased and the TMA became shorter with the increasing inhibitory rate of arachidonic acid pathway（P＜0.05）.The number of cases having no K time was increased when the K time became longer.Conclusion Inhibition of arachidonic acid pathway in platelets is not favorable for clot formation.The speed and strength of clot formation decrease with the increasing inhibitory rate of arachidonic acid pathway.The inhibition rates of arachidonic acid pathway and ADP receptor pathway are positively correlated.