Spatial resolution is an important index in image quality evaluation. Modulation Transfer Function （MTF） is usually used to estimate the spatial resolution fo an image. Because of the image noise and the dispersion character of the sample data

smoothness and interpolation are two necessary links. Thus

the algorithm of smoothness and interpolation will directly affects the result of evaluation. Two algorithms of smoothness and two algorithms of interpolation have been applied to the experiments of evaluating two typical imagery according to eight experiment schemes. The influence machnism of the algorithms on image spatial resolution evaluation has been achieved

and a better algorithm of smoothness and a better algorithm of interpolation have been selected.