In order to detect coagulation factor VIII (FVIII) inhibitor in patients with severe hemophilia A (HA) and preliminarily study the genetic mutation in patients with inhibitor positive. Totally 58 patients with HA (FVIII: C < 1%) were enrolled. FVIII: C activity was measured by one-stage coagulation assay. FVIII inhibitor was screened by using APTT method and FVIII inhibitor in screened positive patients with HA was quantitatively analyzed by using Bethesda method. Using genomic DNA as template, 12, 14, 16 exons of FVIII in screened positive patients were amplified, and the mutations of amplified products were detected by direct sequencing. The results indicated that the FVIII inhibitor could be detected in 4 patients (6.9%) from 58 HA patients, no gene mutations in 12, 14, 16 exons of FVIII were found. It is concluded that the positive rate of FVIII inhibitor in HA patients is lower than that reported in literature. The causes of inhibitor production needs to further investigate.