The dynamic relationship of Zernike modes in an adaptive optics (AO) system using direct-gradient wavefront control algorithm was established. By comparing the power spectra rejection function of those Zernike modes that describe the atmosphere disturbed wavefront, the phenomena of different compensation effect for those Zernike modes in an adaptive optics system using irect-gradient wavefront control algorithm were indicated and the reason of causing different compensation effect was analyzed. The theoretical results were verified using the experimental results on a 61-element adaptive optics system.