In order to use Hartmann-Shack wavefront sensor testing lithography objective lens accurately, two-dimension insert polynomial is proposed to replace Zernike polynomial, which is the basic of modal wavefront reconstruction. The wavefront aberration of a lithography lens is simulated to be the under-test wavefront. The root-mean-square (RMS) value of the reconstruction error reaches 0.0609λ. The possibility of this method is proved. The accurate of reconstruction changes stablely by increase of polynomial fitting orders when the under-test wavefront is ideal spherical wavefront. By reconstructing sine wavefront, cosine wavefront, aspherical wavefront and normal wavefront which contains low order of spherical aberration, coma, astigmatism, field curvature and distortion aberrations, the accuracy of Zernike modal wavefront reconstruction and two-dimension insert modal wavefront reconstruction is compared. A more stable and accurate basic of modal wavefront reconstruction is obtained.