Water-soluble B vitamins are necessary nutrients to maintain the normal physiological function of the human body. Ingestion of proper amount is beneficial to growth, metabolism and development, but excessive intake is seriously harmful to the body. Therefore, the research of vitamin detection methods has attracted the attention of quality control departments and scholars at home and abroad. Traditional microbial, chemical and high performance liquid chromatography (HPLC) methods for vitamin determination have some problems, such as complicated operation, complex sample processing, high cost and so on. It is urgent to develop a B-vitamin detection technology that is simple, fast, and accurate. Special characteristics of terahertz wave make it widely used in the detection of materials. The singular electromagnetic properties of metamaterials and the sensitivity to surface media promote the development and application of terahertz metamaterials in the field of detection. We present an identification method of water-soluble Vitamins B using quad-peak terahertz metamaterials. The sensor consists of an outside aluminum hexagon ring and an inner aluminum circle on high resistance silicon substrate, and are asymmetrically split at the same position deviating from the center of the unit cell. Firstly, the formation mechanism of four peaks and the sensing performance are revealed by using the finite-difference time-domain (FDTD) method, and the frequencies of the four peaks are 0.46, 0.57, 0.66 and 0.90 THz, respectively. During the experiment, the different types of vitamin B (B1, B3, B5 and B6) aqueous solution were dripped on the surface of the metamaterial sensor with the same concentration (0.5 mg·μL-1). The transmission spectra were measured by the THz time domain spectroscopy (TDS) system, and the frequency offsets of four resonance peaks were obtained. The simulation and experimental results show that the sensitivity of the sensor formed by the coupling of inner and outer rings are significantly higher than that of the sensor formed by the oscillation of the electric dipoles of the single outer or inner ring. The four peaks of the sensor can be used for sensing detection, and the sensing sensitivity of the resonance peaks formed by the coupling of inner and outer rings is relatively higher. The asymmetric double-open rings have excellent sensing properties and can be used for sample sensing in biomedicine and other fields.