Abstract: Using brain microdialysis and LC-MS/MS to detect acetylcholine in rat brain to investigate the effects of ligustrazine. A liquid chromatography-tandem mass spectrometry method has been developed and validated for the determination of acetylcholine in rat brain dialysate sampling by microdialysis. The results indicated that ligustrazine administration by subcutaneous injection significantly increased Ach release in rat medial prefrontal cortex and nucleus accumbens in a dose-related manner. The drug’s effect on Ach release in rat brain could be directly detected by microdialysis combined with HPLC-MS/MS and this method is selective and sensitive.