Y-shaped three-way stainless steel three-way is generally used as an auxiliary component of the 13C infrared spectrometer. A Y-shaped three-way component includes a Y-shaped three-way pipe. Two branches in the same direction in the Y-shaped three-way pipe are respectively connected with an instrument connector through the crossover unit structure. The instrument connector of the product is used to plug into the first group of sample sockets of the spectrometer. Branches in the other direction in the Y-shaped three-way pipe are connected with an air bag connector through the crossover unit structure, The air bag connector of the product is used to plug the sample air bag. In the process of instrument quality control, the utility model only needs to plug a sample air bag into the instrument to complete a sample gas detection, which is simple and convenient, improves the working efficiency, and ensures the consistency of 13C abundance of sample gas.