Objective：To investigate the infection status of hepatitis B virus and the immune state of children admitted to our hospital. Methods：Totally 21 473 children in the outpatient department，hospitalized department and the physical examination center of the children’s hospital of Chongqing medical university in 2009 were enrolled in the study. Statistical analysis on the examination results of HBV serology markers was conducted in clinical laboratory center. Results：The positive rate of HBsAg was 1.4%（301/21 473） in children，including 1.1%（228/21 473） with both positive HBsAg and positive HBeAg and 0.3%（73/21 473） with positive HBsAg but negative HBeAg. The positive rate of anti-HBs was 51.2%（10 990/21 473）. The positive rate of anti-HBe and/or anti-HBc was 7.0%（1 501/21 473）. The negative rate of HBV serologic markers was 40.4%（8 681/21 473）. Conclusions：In 2009，the HBV infection rate of children in Chongqing was 1.4%，lower than that of common crowds in the whole country in 2005. The positive rate of anti-HBs was 51.2%，higher than that of common crowds in the whole country in 2005. The positive rate of HBsAg and/or HBeAg，especially anti-HBs is relatively high，frequent follow-up should be conducted in children.