Abstract: OBJECTIVE To establish a method for detection of aceclofenac in increasing bone density health food by ultra-high performance liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS). METHODS The separation and analysis was performed on an Agilent Eclipse Plus C₁₈ column(2.1 mm×50 mm, 1.8 μm). The mobile phase consisted of methanol-0.1% acetic acid containing 10 mmol·L^-1 ammonium acetate(70:30). Electrospray ionization(ESI) source was applied and operated in the positive mode. Multiple reaction monitoring(MRM) mode was used to quantify aceclofenac. RESULTS The assay linearity of aceclofenac was confirmed over the range of 5.0-100.0 ng·mL^-1(r=1.000 0). The average recovery of aceclofenac was 99.1% and RSD was 0.25%. The repeatability of RSD was 0.4%. The LOQ was 1.8 μg·kg^-1. CONCLUSION The method is proved to be specific, sensitive and accurate. Therefore, it can be used to detect aceclofenac illegally added in increasing bone density health food.