The high accuracy of Fabry-Perot (F-P) etalon interval d has a very important influence on the interference measurement. Based on F-P interference imaging information, combined with the local subdivision principle of the peak coordinate and the regression of circular equation, in particular, a new method of virtual plane pixel subdivision and signal smoothing was applied, and the concentric ring diameter Di was obtained accurately. Then the accurate calculation of the decimal part and the integer part of the interference order was realized, and the measurement of the interval d by excess fraction method with three-standard wavelengths was completed. In addition, the influence of subdivision and non-subdivision on measurement results was analyzed. With the virtual pixel subdivision, the interval d is (2 009.961 91±0.000 06) μm, and (Uε/k0) is 9.8×10-7.Experiments verify the effectiveness of pixel subdivision method, providing effective ways to improve the accuracy of interval d.