In order to determine the acceptability of dielectric coating, uncertainties estimations of reflection coefficients are studied using discontinuous Galerkin time domain (DGTD) method. According to the probability statistic theory, the mean and variance of reflection coefficients are calculated. The computed quantities of interest are compared with analytic solutions, and good agreement for the statistics is observed, especially between the larger order of approximation and the number of elements, as demonstrated by the numerical experiments.