This paper deals with the interferometric thickness measurements of spin-coated thin polymer films. Spin coating is currently the predominant technique employed to produce uniform thin films of polymers in sub-micrometer range. But the thickness measurement of such thin films requires the application of high precision methods. In the paper we design and develop the system based on the common interferometer MII-4 and digital camera for measurement of the thin PEPC and PETPC polymer films. Different concentration of polymer solution and spin speed were used in order to obtain thin films with variable thickness (from 100 nm to 1000 nm) by spin coating technique.