Abstract: With the development of coating machine and film coating technology, film coating has become the mainstream of tablet coating. Coating thickness is an important index to measure the coating effect, and affects the quality of drug directly. In this paper, microscopic image measurement method, near infrared spectroscopy method, Raman spectroscopy, X-ray fluorescence spectroscopy and terahertz spectroscopy method of film coating thickness are briefly analyzed, and we compared the advantages and disadvantages of various methods of measurement. The results show that terahertz spectroscopy method is the most effective method.