Bisphenol F (BPF) and its derivatives have a wide range of applications in plastic, coating and other important chemical industries. However, the parallel-consecutive reaction feature makes the synthesis of BPF very complicated and difficult to control. Precise control of the process is the key to a safer and more efficient industrial production. Herein, an in situ monitoring technology of BPF synthesis based on spectroscopy (attenuated total reflection infrared, Raman) was established for the first time. Using quantitative univariate models, the mechanism and reaction kinetics were studied in depth. Moreover, a better process route with a relatively low phenol/formaldehyde ratio was optimized with the in situ monitoring technology established, which could be used for much more sustainable scaled-up production. The present work could lead to application of in situ spectroscopic technologies in chemical and pharmaceutical industries.