Objective: To develop a LC-MS method for the determination of EXH-1626 in rat plasma. Methods:Using carbamazepine as internal standard (IS),plasma samples were deposited by blood precipitation reagent(methanol∶5% zinc sulfate =70∶30,V/V) before sampling and determined by injecting 5 μl supernatant to LC-MS system. Chromatographic condition:the analytes were separated on a Han Bang ODS C18(5 μm,150 mm × 4.6 mm) analytical column with acetonitrile and 10 mmol/L ammonium acetate(using acetic acid to make pH = 3) (70∶30) as the mobile phase. Analysis was performed at a flow rate of 0.6 ml/min and the column temperature was 30℃. Mass sapectum determination was performed in electrospray ionization(ESI) mode and the selected ion monitoring(SIM) mode,EXH-1626 was monitored at m/z 453.3 and internal standard at m/z 274.3. Results: The linearity of EXH-1626 concentration curve was in a range of 5~1.0 × 104 ng/ml,r = 0.999 7,and the lowest limit of quantification(LOQ) was 5 ng/ml. The RSDs of inter-day and intra-day were less than 10%,absolute recoveries were greater than 70%,and relative recoveries were between 90% to 110%. Conclusion:The method is proved to be fast,precise,sensitive,convenient,and suitable for determination of concentration and non-clinical pharmacokinetic study of EXH-1626.