The dissolution of Mn ions from Mn-containing cathodes and the growth of Na dendrites are two critical issues that deteriorate the life time of Na batteries. In this work, we develop a novel solid-state composite-polymer-electrolyte based on a polyvinylidene fluoride matrix and Na3Zr2Si2PO12 fillers to simultaneously tackle these two problems. Elemental and morphology analysis show that the composite-polymer-electrolyte effectively impedes the dissolution and migration of Mn ions from the Na0.67MnO2 cathode as well as facilitates the uniform deposition of Na on the anode. A facile interface modification is applied to improve the contact between the composite-polymer-electrolyte and electrodes, which reduces the interfacial resistances and greatly delays the growth of Na dendrites. Consequently, the Na0.67MnO2/Na cell with the composite-polymer-electrolyte displays a significant improvement in cyclic stability and rate performance, without sacrificing the specific capacity, compared to that of a cell using an organic-liquid-electrolyte. Therefore, this work provides an effective way to improve the cycle life of Na batteries by stabilizing both electrodes with a composite-polymer-electrolyte and can be readily applied to other batteries, e.g. Li batteries.