OBJECTIVE： To establish a method for the determination of dexlansoprazole concentration in plasma of Beagle dogs， and to evaluate bioequivalence of 2 kinds of Dexlansoprazole sustained-release capsules. METHODS： A total of 6 Beagle dogs were randomly divided into reference preparation group and test preparation group， with 3 dogs in each group. In double cycle cross randomized trial （cleaning period lasting for one week） design， they were given reference preparation and test preparation of Dexlansoprazole sustained-release capsules 60 mg once. The blood sample 2 mL of forelimb vein were collected before medication， 0.5， 1， 1.5， 2， 2.5， 3， 3.5， 4， 4.5， 5， 6， 7， 8， 10， 12 h after medication， respectively. The concentration of dexlansoprazole in plasma of Beagle dogs was determined by LC-MS/MS. Using omeprazole as internal standard， the determination was performed on Inertsil ODS with mobile phase consisted of methanol-0.1％ formic acid solution （90 ∶ 10，V/V）. ESI was used for positive ion scanning by multiple reaction monitoring mode. The ion pair for quantitative analysis were m/z 369.9→251.7 （dexlansoprazole） and m/z 345.7→197.9 （internal standard）， respectively. The pharmacokinetic parameters were calculated by using DAS 3.1.6 software. The bioequivalence of two preparations were investigated by bilateral t test，（1-2α）confidence interval （CI） method and Wilcoxon test. RESULTS： The linear range of dexlansoprazole concentration was 10-4 000 ng/mL. The lower limit of quantitation was 10 ng/mL； RSDs of inter-batch and intra-batch were lower than 10％. The accuracy ranged 94.40％-105.20％. The pharmacokinetic parameters of reference preparation or test preparation of single fasting dose were as follows： AUC0-t were （8 892.48±1 399.67），（8 683.71±1 167.88）ng·h/mL，AUC0-∞ were （8 925.73±1 399.64），（9 053.08±1 553.46）ng·h/mL，tmax were （3.50±0.71），（3.75±1.21）h，cmax were （2 980.00±487.40），（2 863.33±331.34）ng/mL， respectively. 90％CI of AUC0-t， AUC0-∞ and cmax for test preparation were 80％-125％ of corresponding parameters of reference preparation； there was no statistical significance in tmax between 2 preparations（P＞0.05）. CONCLUSIONS： LC-MS/MS is suitable for the determination of dexlansoprazole concentration in Beagle dogs plasma. Moreover， the two preparations are bioequivalent in Beagle dogs．