Vitamin B12 (VB12) is essential to human metabolism, the formation of red blood cells, and the maintenance of the central nervous systems.It is usually regarded as important biomarker that indicates a disease status.Its normal concentration in human plasma falls in the range of 100-300 pg/mL and lower content is observed under disease status resulting from VB12 deficiency.Selective and sensitive analysis of VB12 in biological fluids is of paramount significance to clinical diagnosis.In this research, a robust approach for rapid and sensitive determination of VB 12 in human plasma was developed.Quantitative analysis and qualitative confirmation can be achieved in single injection due to the novel Triggered MRM function which can provide MRM chromatogram for accurate determination purpose and composite MS/MS spectrum for confirmatory analysis by spectrum matching strategy.