Abstract: The simultaneous determination of residual avermectin (AVB), doramectin (DOR) and ivermectin (IVR) in eel were menswated by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted by acetonitrile, and was cleaned up with an alkaline column of alu mina oxide after the procedure of concentration. The detection was performed by tandem mass spectrometry with electrospray ionization in positive mode (ESI⁺). The time for the determination of the above three pesticides was only 4.2 min. The results show that the standard curves for the above three avermectins pesticides are linear, and their correlation coefficients (r) is more than 0.99 in the range of 0.5-20 μg•kg^-1. The average recovery is ranged from 85.9% to 94.4%, and the relative standard deviation (RSD) is less than 8%. The limits of quantity (S/N ≥ 10) by the present method for avermectin, doramectin and ivermectin are 0.43, 0.48 and 0.32 μg•kg^-1.