Objective To analyze the relationship between hepatitis B virus (HBV)DNA load and serum alanine aminotransferase (ALT) level and to investigate the reason that ALT level changes in patients with HBV infection.Methods ALT level (dependent variable)and HBV DNA load (independent variable)were subjected to curve fitting using SPSS 16.0 to establish a curve regression equation and analyze the curve regression equation.Results A power model was established by software analysis,with the following results:R2 =0.107,F=85.887,P=0.000,b0 =47.785,b1 =0.075,b2 =0.The curve analysis showed that as the HBV DNA load increased,the ALT level kept rising,but at a decreasing rate;within a certain range,the increase in HBV DNA load led to little change in ALT level,which was infinitely close to a certain value.Conclusion ALT level is correlated with HBV DNA load,but HBV DNA may not be the most direct cause of change in ALT level.