In this paper, we use the bilateral filter to de-noise nighttime infrared monitoring images, in order that noises are reduced and edges are preserved. Considering that traditional bilateral filter does not balance gray-scale difference and the geometric distance in determining the weights of convolution kernel coefficients, we propose to give the two different values different weights, so that both of them are fully considered. Experimental results show that this algorithm can effectively remove noise as well as perfectly retain edge information.