Objective To investigate mutations at HBV P gene RT region in lamivudine-resistant patients. Methods Serum samples were collected from 74 hepatitis B patients resistant to lamivudine. HBV P gene RT region was amplified by PCR, and the PCR products were directly sequenced and the viral loads were detected. Results There were 7 forms of mutations in 74 patients harboring YMDD mutations detected in this study. The common mutation forms were rtM204V/rtL180M, rtM204I and rtM204I/rtL180M. The most frequent mutation positions were rtM204I (38.7%), rtM204V (21.8%), rtL180M (38.7%) and rtV173L (0.8%). Conclusions The mutation forms and positions of lamivudine-resistant viral strains are complex. Common mutation forms and positions are not directly correlated with the viral load, but some novel forms may be associated with it.