A study was carried out to determine the coefficient of friction for some varieties of rice, corn, wheat and barely at five different levels of grain initial moisture content. A digital instrument was used for the experimental measurements using nine different friction surfaces of plywood, rubber, galvanized iron, normal iron, painted iron, stainless-steel, wire-net, perforated iron and plastic. The obtained results showed that, the coefficients of friction for the four studied crops were increased with increasing grain moisture contents and roughness of grain surface. The recorded friction coefficients were ranged from (0.3542 to 0.3765), (0.2415 to 0.6128), (0.2519 to 0.6988) and (0.2481 to 0.6927) for rice, corn, wheat and barely, respectively. Also, for all the tested crops rubber, perforated iron and wire net surfaces recorded the highest values of friction coefficients, normal, painted and galvanized iron surfaces recorded a moderate values, while plywood, plastic and stainless steel surfaces recorded the lowest values. The statistical analysis revealed a highly significant linear positive relationship between the grain moisture contents and the coefficient of frictions for all the studies friction surfaces.