The invention relates to a liquid detection method of Suvorexant and isomers thereof, belonging to the technical field of separation and detection. According to the detection method, by using a chromatographic column (poroshell 120EC-C18, 4.6mm*100mm, 2.7 microns), isocratic elution is carried out at a certain condition by using a perchlorate aqueous solution, methanol or acetonitrile as a moving phase, wherein the pH of the moving phase is 2.5. The method can be used for effectively separating and detecting Suvorexant and isomer impurities thereof, and the chromatographic peak is good in peak pattern, short in peak appearance time and good in degree of separation and specificity.