A sensitive and specific LC-CMS/MS method was developed for the quantification of changrolin, an anti-arrhythmic drug, in rat plasma using tiapride as internal standard. Liquid-liquid extraction was employed for sample preparation and analyzed using a multiple reaction monitoring mode with electrospray positive ionization source. The calibration curve for changrolin was linear over the range 5-1600 ng/mL with coefficients of correlation >0.99. The intra- and inter-batch precision was less than 8.6%, and accuracy ranged from 94.6% to 104.5%. This validated LC-MS/MS method was successfully applied to a bioavailability study of oral and intravenous administration of changrolin with 20mg/kg dosage in SD rats.