A reaction control and mass spectrometry workstation for coupling an X-ray spectroscopic characterization instrument with an in-situ reaction cell, including a reactant gas composition control module and an online gas composition analyzing module. The workstation further involves a modification based on the original vacuum pipeline section. After the modification, the original vacuum pipeline section is connected to three customized gas ports, and the modification is characterized in that the vacuum manifold unit is additionally provided with a mass spectrometer sampling port, a sampling capillary, and control valves. The present disclosure has the following advantages. The sampling time delay can be ignored in the mass spectrometry, and the sampling is continuous real-time in-situ analysis with high time resolution. Under the working conditions of the X-ray spectroscopic characterization instrument, the electronic structure/crystal structure information and the precise information of the ambient gas composition are obtained simultaneously.