To explore the prognostic significance of hidden blood loss in total hip arthroplasty.From May 2008 to July 2009, Harris hip score was used to evaluate the functions of 71 patients undergoing single side total hip arthroplasty (including 47 males and 24 females with a mean age of 68.3 years, ranged from 48 to 75 years). The blood loss in the operation was analyzed to study the correlation between hidden blood loss and the functional rehabilitation.All 71 patients undergoing THA were involved in the result analysis. The mean total blood loss was 1473 ml and the hidden blood loss was 545 ml (37%). Hidden blood loss significantly correlated with functional rehabilitation (P = 0.001), but there were no correlations between functional rehabilitation and age, gender, operative limb of patients (P = 0.067, 0.527, 0.926, 0.072).Hidden blood loss maybe a useful prognostic information contributing to the functional rehabilitation of total hip arthroplasty.