The invention discloses a kit for detecting 15 bile acids in serum and an application of the kit, and belongs to the technical field of blood detection. The 15 bile acids comprise a cholic acid, a glycocholic acid, a taurocholic acid, a lithocholic acid, a glycolithocholic acid, a taurolithocholic acid, a deoxycholic acid, a glycodeoxycholic acid, a taurodeoxycholic acid, a chenodeoxycholic acid,a glycochenodeoxycholic acid, a taurochenodeoxycholic acid, an ursodeoxycholic acid, a glycoursodeoxycholic acid and a tauroursodeoxycholic acid. The kit comprises an eluent, a calibration product solution, a mixed internal standard working solution, a protein precipitant and a quality control product. When the kit is used for detecting the bile acids in the serum, a to-be-detected sample does notneed derivatization treatment, pretreatment is simple, a sample dosage is small, sensitivity is high, specificity is strong, more types can be detected, the 15 types of bile acid can be simultaneously detected within 6.5 minutes, and the kit can be used for clinical diagnosis and health assessment of serum bile acids.