Abstract: This paper describes in detail the relationship between the resoluttion, signal to noise ratio and the experimental data from EXAFS measurement.It has been presented the opinion of critical condition for experimental data and the method of a precise measurement. The relationship between resolution, singnal to noise ratio and the critical experimental data have been discussed and the following conclutions have been introduced at the critial condition:
1. The resolution is independent on the rocking curve width of the monochromator crystal when the width of entrance slit and exit slit both equal to the critial data but the signal to noise ratio depends on which is more important to the mosaic structure size that is characte-rized by the rocking curve wicth of the mono-chromactor crystal:the intensity distribution or the extinction effect.
2. The entrance slit width increases to the optimum that the resolution keepsa constant and the signal to noise ratio increase obviously wh the width of exit slit and the rocking curve of monochromator crystal equal to the critical data. But the signal to noise ratio does not in crease with the entrance slit width if the width is largerth an the op timura.
It has been shown in the paper that the conclution 1 is more suitable to that where the perfection of the monochromator crystal is not good enoughi and the conclution 2 is fit to perfect crystal.