Abstract: A method was developed for the determination of 8 neonicotinoids in seawater by automatic solid phase extraction, ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS). After the samples were enriched, purified and concentrated by solid phase extraction (SPE), the samples were analyzed by ESI and multiple reaction selective ion monitoring (MRM) mode, and quantified by internal standard method. The results showed that 8 neonicotinoids had a good linear relationship in the range of 100−5000 ng/L (r² > 0.9990), the detection limit of the method was between 0.08−0.14 ng/L, and the determination limit was between 0.32−0.56 ng/L. The recoveries of low, middle and high levels were 81.5%−98.5%, 83.7%−96.8% and 83.1%−96.9%, respectively, and the relative standard deviations were 3.0%−7.8%、2.1%−8.8% and 2.6%−8.7%, respectively. The method was used to detect 12 seawater samples in coastal waters, and a total of 5 neonicotinoids with different concentration ranges were detected, the concentration range was nd−82.1 ng/L, and there was no obvious interference in MRM channels of each substance detected. The method has the characteristics of low detection limit, good sensitivity and high accuracy, and is suitable for the detection of neonicotinoid pesticides in seawater.