Based on Zernike polynomials fitting wavefront, an algorithm of calculating Zernike coefficients for any wavelength transmitted wavefront at defocus position was put foward. The method compensates the change of Zernike coefficients of defocus distance based on Zernike coefficients at focus position. Using an achromatic system, the working position was optimized according to the wavelengths and weights, and the defocusing amount between focus position and working position was calculated, and the any wavelength wavefront Zernike coefficients at working position was verified by the algorithm. The result showed that the proposed algorithm is effective for calculating Zernike coefficients related to position, compared with using Conrady-Zernike formula in working position, the absolute error of Z1 decreased from 6.78 to 1.41, and the absolute error of Z4 decreased from 6.83 to 1.45.