Objective To explore the pharmacokinetics of self-made gliclazide modified release tablets in Beagle dogs and to evaluate the in vivo and in vitro correlation. Methods Six Beagle dogs were orally given self-made gliclazide modified release tablets or reference preparation (DaMeiKang) at a dose of 30 mg with self-control cross-over method. Blood samples were collected at different time points after administration. The gliclazide concentration in plasma was determined by high-performance liquid chromatography, and the pharmacokinetic parameters were calculated. The pharmacokinetic characteristics and relative bioavailability of self-made gliclazide modified release tablets were investigated, the bioequivalence was evaluated, and the in vivo and in vitro correlation was calculated. Results Area under curve (AUC_0-∞) of DaMeiKang was (101.74±20.29) μg/(mL·h), and AUC_0-∞ of self-made gliclazide modified release tablets was (95.40±28.68) μg/(mL·h). There were no significant differences in the pharmacokinetic parameters between the test and reference formulations (P>0.05). The relative bioavailability of self-made gliclazide modified release tablets was 93.77%, which was bioequivalent with the reference preparation. The in vitro and in vivo correlation analysis showed that the correlation coefficients of DaMeiKang and self-made gliclazide modified release tablets were 0.912 and 0.894, respectively, which were higher than the critical value (r_{0.05, 7}=0.754). The in vitro release rates of the two preparations were correlated with the in vivo absorption rates. Conclusion The self-made gliclazide modified release tablets have sustained-release characteristics and bioequivalence with reference preparation. The in vivo absorption behavior of gliclazide modified release tablets can be predicted by the in vitro release assay established in this study.