Objective:To evaluate the accuracy of determinating fibrinogen with Prithrombin time derived.Methods:The plasma fibrinogen of 113 patienss were determined by PT and recorded the derived fibrinogen,compared with the fibrinogen results of CLAUSS methed.Results:The within cv of PT derived fibrinogen was 3 5%.When the fibrinogen determination of PT derived was 1 50~2 99g/L,P0 05;when the fibrinogen was 3 00g/L, P 0 01,the results of PT derived fibrinogen were higher than the results of CLAUSS method.Conclusion:Plasma fibrinogen determination of PT derived is simple,economical,but not suitable for clinical application if the fibrinogen of PT derived result was over 3 00g/L.