Abstract: An ultra performance liquid chromatography-tandem mass spectrometric method was developed for the determination of the four non steroidal anti- inflammatory drugs (Meloxicam, Flunixin, Carprofen and Tolfenamic Acid) in porcine muscle. The drugs were extracted with acetonitrile, then cleaned-up by liquidliquid extraction with n-hexane, and finally analyzed by ultra performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) in multiple reaction monitoring (MRM) mode via positive electrospray ionization. The method was validated at three fortification levels (LOQ, 2.5LOQ and 5LOQ) in porcine muscle. The validation results were as follows: the correlation coefficients of the standard calibration curves for the four non- steroidal anti- inflammatory drugs all were 0.999 over their own concentration range; the average recoveries of the four drugs were between 72.1% and 87.3% , with the relative standard deviation (RSD) between 2.8% and 6.7% ; the limits of quantification (S/N≥10) of Meloxicam, Flunixin, Carprofen and Tolfenamic Acid were 1.6, 1.6, 80 and 8.0 μg/kg. It was indicated that the method developed in this study is cheap，easy and has a good purification effect. The sensitivity, accuracy and precision of the method were all acceptable, and it can meet the requirements of the multiple residue analysis. So, this method can be further applied to investigate the anti-inflammatory residue status in porcine muscle.