Abstract: AIM: To study the ways of calculating area under the plasma concentration-time curve (AUC) in non-compartment model pharmacokinetics by comparing the accuracy & precision of every method.  METHODS: Three methods were used to calculate the area under 0-T curve (AUC0-t) in G drug equivalence test. (1) Linear method (2) Linear/Log method: Data before the maximum blood concentration (Cmax) was calculated by the linear trapezoid rule, and those after Cmax by logarithmic trapezoid rule (3) Linear Up/Log Down: The ascending part of the curve was calculated by the linear trapezoid rule, and the descending part by logarithmic trapezoid. Equivalence criterion of AUC0-t after logarithmic transformation is 80.0%-125.0%, and differences between three methods were compared on simulated data. RESULTS: Both the AUC0-t and equivalence analysis results show difference between three methods, in these 24 subjects took G drug of two preparations. Furthermore, Linear and Linear Up/Log Down method have the equivalent conclusion, while not the Linear/Log method. AUC0-t showed great difference in small sample of simulation data, contrast to slight difference in the large sample data case. CONCLUSION: Linear Up/Log Down method is more appropriate for oral administration and multi-peak curves，and Linear calculation is more effective to get stable results in small sample size test or pre-test，while Linear/log method is not so often used. In addition, bioequivalence research should be included in AUC calculation in the analysis plan.

Key words: area under the plasma concentration-time curve (AUC), bioequivalence, pharmacokinetics