To detect salient motion in a snow or rain weather in outer-door condition,and avoid the large noise,this issue present a new method as temporal approach in infra video images.Assume there exist a linear relationship between difference temporal frames in video queue,and the equations are inconsistent because of the attending of noise.Through Chebyshev approximation in Banach space,coefficients be get to the equations.By setting adequate threshold on the solution coefficients,we can not only detect the salient motion but eliminate the noise motion.Exert the algorithm to real situation,the experiment result shows that the method is more precise and better robustness than simple temporal subtraction.