Objective:To establish a determination method of palonosetron level in plasma. Methods:LC conditions were as follows: Hypersil GOLD(150 mm × 4.6 mm, 5 μm)was used with the mobile phase consisting of acetateamine buffer (0.1% formic acid )-method(50∶50). Equipped with an atmospheric pressure chemical ionization(APCI) source was used as detector. The plasma samples added with internal standard were extracted with Acetic Ether, then concentrated and determined by LC-MS/MS. Results:The linear range of palonosetron was 0.04~20.00 ng/ml . The lower limit of quantification(LLOQ) was 0.04 ng/ml. The recoveries of palonosetron at low, middle and high concentration and the intra-day and inter-day RSDs all met the standards. Conclusion:The established method is sensitive, specific, reproducible and suitable for studies of pharmacokinetics and detection of plasma drug concentration of palonosetron.