Abstract: According to the law of light intensity distribution in the interferencefield, an expression for the distribution of light intensity in the Newton's rings isderived. By use of the error analysis, some conclusions are obtained. The spacingbetween two fringes has no effect upon the error of measurement of the curvatureradius R,and for processing experimental data the weighted mean and its standarddeviations must be used, at the same time, two new deductions are obtained.