Due to the coupling of micromachined membrane deformable mirror (MMDM) is much larger than that of the common deformable mirror. The voltage-decoupling model for a 37-channel MMDM is established through theoretically and experimentally analyzing the principle of fitting aberration of a continuous-surface deformable mirror. The fitting error for the first 10-order Zernike mode is carried out by means of the measured influence function of and coupling among actuators. The index and width of Gaussian function which is used for fitting the influence function is calculated. The experiment result demonstrate that Zernike mode can be act as the control voltage decoupling algorithm for the adaptive optics system based on MMDM.