Bilateral filtering can effectively smooth SAR images with the edges preserved, but it is difficult to optimally configure the parameters of bilateral filtering. Traditional method is based on an optimal trade-off hypothesis according to the despeckling estimation indexes, including the equivalent number of looks (ENL) and edge preserving index (EPI). However, the variance of gray value similarity obtained by traditional method has large error, and to improve accuracy, the computing time is increased linearly. In this paper, we present a novel method to configure the parameters of bilateral filtering based on the hypothesis and the monotone properties of the ENL and EPI curves. Experimental results show that the accuracy of variance of gray value similarity is increased by one order of magnitude in the case of almost the same computing time; the computing time is reduced by one order of magnitude for the same accuracy of variance of gray value similarity.