Abstract: Objective　To investigate the relationship between platelet (PLT) parameters and age，sex，hepatitis B virus (HBV) DNA load and other factors.   Methods　A total of 878 hepatitis B surface antigen (HBsAg) positive patients were enrolled for the determinations of PLT count，thrombocytocrit(PCT)，mean platelet volume (MPV)，platelet distribution width (PDW)，HBV DNA and alanine aminotransferase(ALT)/ aspartate aminotransferase (AST). Variance analysis，regression analysis，one-way ANOVA and 2-sample t-test were used to analyze the data statistically. Results　Factorial analysis demonstrated age，sex and HBV DNA would influence PLT parameters，but ALT/AST would not. PLT and PCT were lower in HBsAg positive patients than in healthy subjects with same age and sex，while MPV and PDW were higher. There was a negative relationship of PLT and PCT with HBV DNA in elderly HBsAg positive patients，while MPV and PDW had no correlation. The 4 PLT parameters in young and middle-aged subjects had no correlation with HBV DNA. Conclusions　PLT and PCT decrease with the increase of HBV DNA load in HBsAg positive patients over 50 years old，which may be related to the suppression or destruction of megakaryocyte differentiation and growth with the increase of HBV DNA load. Monitoring the PLT parameters is of benefit to monitor the hemostatic and coagulative conditions in the patients.

Key words: Hepatitis B virus, DNA, Platelet count, Thrombocytocrit, Mean platelet volume, Platelet distribution width