It was found that the response of grained La0.67Ca0.33MnO3 films to microwave radiation is of thermal nature. A nonresonant method for measuring of the electric resistance of grains was developed. It allows one to avoid the influence of the magnetic field of the wave on the measurement results. The measurements of the temperature dependences of the grain electric resistance indicate that in the vicinity of the maximum-resistance temperature Tm, the intrinsic electric resistance of the grains is more than by two orders of magnitude lower than the film resistance measured by applying the dc current. The obtained experimental results agree well with those given by resonant techniques.