Based on the technology of digital precision forming machine without pattern casting,digital extrusion method of sand mold is proposed to get near-net forming sand mold innovatively. Optimization algorithm of sand mold forming with digital flexible extrusion technology is studied. The maximum volume formula,with sand mold cavity attitude and position as variables,enveloped by extruding units envelope surface, V(α, X, Y)_max is established as objective function. And,the restrictions are analyzed. Optimized results of sand mold formed by digital extrusion technology are obtained by numerical iteration method. Extruded sand mold,formed close to the target one,is got by digital flexible extrusion technology with the optimization algorithm. And,near-net forming sand mold with digital flexible extrusion technology are achieved.