The cubic phase mask is used to extend the depth of field in a wavefront coding system,the point spread function is asymmetric. We research a new iteration algorithm to get the final sharp color image,which based on the GMRES (generalized minimal residual methods) combined with the regularization method and multichannel processing procedure. In order to eliminate the ringing effect,Antireflective boundary conditions and Kronecker product approximation is used for the new image formation. Analysis and the simulation show that the new algorithm can give excellent deconvolution results and suppress the noise magnification effectively. From the experimental result,this new algorithm can give better results than classic Wiener filtering with little ringing effect on the image border and little vibration on the edge.