Abstract: Sample of edible flavoring oil was extracted with acetone, the extracting solution was taken for purification by MCX cation solid phase extraction column. The rhodamine B was eluted from column with a mixture of ammonia (aq.) and methanol (5+95), and evaporated to near-dryness by N2-blowing and made up to 2 mL with methanol. ACQUITY BHE C18 column was used as stationary phase, and the mixture of methanol and 0.1%(φ) formic acid solution with different ratio was used as mobile phase in gradient elution. ESI and multi-reactions monitoring mode were adopted in MS/MS. Linear relationship between values of peak area and mass concentration of rhodamine B was kept in the range of 1.00-100 μg·L-1, with values of detection limit (3S/N) of 0.003 mg·kg-1. Tests for recovery were made at the concentration levels of 0.01, 0.05, 0.20 mg·kg-1 of rhodamine B standard, giving values of recovery in the range of 82.1%-97.2%, with RSD′s (n=6) less than 9%.