Adaptive optics (AO) system based on stochastic parallel gradient descent (SPGD) method compensates a beam′s wave-front aberrations by controlling a wave-front corrector with direct optimization of the system′s performance metric. A new method of subzones coupling for modifying the conventional SPGD AO system is presented to increase the convergence speed of the model-free adaptive optics system. A new lower-resolution subzonal wave-front corrector can be approximated by subdividing the wave-front corrector′s aperture into multiple subzones, all actuators associated with each subzone being treated as a whole controlling element. The coupling architecture of double wave-front correctors can be constructed by simultaneously controlling the approximated wave-front corrector and the original one with SPGD technique for a common performance metric. A numerical simulation model for an adaptive imaging system with 256-elements pixelated piston-type wave-front corrector was built up. The numerical simulation results show that this SPGD AO system based on subzones coupling holds faster convergence speed and better asymptotic normality than the conventional SPGD AO system.