In this paper experimental and numerical methods were used to analyze the ribbing phenomenon of forward roll coating process. In experimental approach,two different test fluids, four kinds roll speed ratios and
two gaps were tested by using a two rolls coating machine to measure the coating film thickness and the wavelength of ribbing. In numerical simulation,three-dimensional numerical model and free surface volume of fluids (VOF) module were adopted to calculate the thickness of coating film, wavelength of ribbing and pressure profile of fluid between two rigid rolls. Experimental results showed that increasing the roll speed, decreasing the roll gap and choosing fluid with high viscosity caused more ribbing on roll coating film. Numerical results were in good agreement with experimental tendency and the error between them was about 5% to 10%.