The work aims to study the on-line monitoring method for the coating thickness in the actual coating. Based on the non-Newtonian fluid, the mathematical derivation and theoretical analysis of immersion coating process were carried out. The coating head experimental platform for small-scale immersion roller coatings could analyze and process the images regarding the meniscus formed in the transfer process of coating solution and the coating thickness of immersion roller. The experimental platform that can monitor the coating thickness and quality of coating equipment on-line in real time is designed and it can be well applied in the actual production.