Objective To analyze the hidden blood loss following primary total hip arthroplasty (THA) and put forward corresponding treatment measures.Methods A retrospective study was done on the 138 patients with hip disease managed with THA for the preliminary unilateral replacement from January 2009 to January 2011.There were 48 males and 90 females,at age range of 45-71 years (mean,62 years).The pre-and post-operative blood routine and intra-and post-operative blood loss and transfusion were analyzed and hidden blood loss during peri-operation period was evaluated.Results All the patients were trnsfused with autologous blood intra-operatively.Intra-operative blood loss was (495 ± 105) ml and postoperative drainage volume was ( 121 ±29) ml.In addition,116 patients were given red cell suspension (RCS) and blood plasma to raise the level of hemoglobin and the RCS transfusion volume was (600 ± 225) ml.The total blood loss was (1 521 ±156) ml including hidden blood loss of (822 ±96) ml (57.2％).No obvious differences were observed in the indicators between males and females.Conclusions Hidden blood loss is an important factor that affects the prognosis of the patients treated by THA.In order to secure their safety in perioperative period and benefit their recovery,assessment of the amount of bleeding in THA should fully take the hidden blood loss into consideration and prompt treatment measures should be taken to fully and effectively recover their effective circulation blood volume.