Zernike modal wavefront reconstruction algorithm was used commonly for Hartmann Shack sensor in circle apertures. Formulas to calculate the modal wavefront reconstruction error of Hartmann Shack sensor in general condition were deduced. An aberration plate containing random static wavefront aberrations was measured with a Hartmann Shack sensor and a ZYGO interferometer respectively, then the modal wavefront reconstruction error of Hartmann Shack sensor while using different Zernike polynomials was obtained. The experimental results were analyzed and compared with theoretical calculations.