BACKGROUND Tanshinones are a major class of bioactive ingredients in the traditional herbal medicines, Danshen (Salvia miltiorrhiza). A sensitive and reliable determination method for tanshinones is useful to ensure the quality of Danshen. OBJECTIVE To develop a sensitive and selective analytical method for tanshinones by high-performance liquid chromatography (HPLC) with fluorescence detection after pre-column derivatisation. METHODS The proposed method depends on derivatisation reaction of tanshinones with 4-carbomethoxybenzaldehyde and ammonium acetate forming intensely fluorescent imidazole derivative. RESULTS The proposed method provided excellent sensitivity with the detection limits of 3.3 nM (66 fmol/injection), 3.2 nM (64 fmol/injection) and 2.0 nM (40 fmol/injection) for cryptotanshinone, tanshinone I and tanshinone IIA, respectively, without the necessity of complicated instrumentations. The developed method is successfully applied to quantify the contents of tanshinones in Danshen. CONCLUSIONS The developed method is the first analytical method for tanshinones by fluorescence detection. Since the derivatisation reaction is selective for the o-quinone structure of tanshinone, the developed method will become a suitable mean for the discovering of tanshinone type diterpenoids from herbal samples. Copyright © 2017 John Wiley & Sons, Ltd.