Synthesis and testing of chitosan/PEG4000 solid electrolyte polymer membrane with LiCF 3 SO 3 salt as a surfactant was carried out to determine crystalline size and type of structure using X-Ray Diffraction (XRD) and dielectric constant using Electrochemical Impedance Spectroscopy (EIS). The manufacture of chitosan/PEG4000 electrolyte polymer membrane with LiCF 3 SO 3 salt using the solution casting method. The samples used in the XRD and EIS tests were in the form of solid electrolyte polymer membranes of chitosan, chitosan/PEG4000 and chitosan/PEG4000 with LiCF 3 SO 3 salt. XRD test showed that the crystalline size of the chitosan, chitosan/PEG4000, and chitosan/PEG4000 electrolyte polymer membranes with LiCF 3 SO 3 salt experienced a 2θ angle shift and formed a semicrystalline phase. The peak intensity increase occurred after chitosan was added with PEG4000 with LiCF 3 SO 3 salt. The crystalline size obtained for the electrolyte polymer membrane of chitosan, chitosan/PEG4000 and chitosan/PEG4000 salt LiCF 3 SO 3 was 4,002 nm; 2,474 nm and 4,183 nm. Meanwhile, the type of structure produced by chitosan, chitosan/PEG4000 and chitosan/PEG4000 electrolyte polymer membranes with LiCF 3 SO 3 salt is a semicrystalline phase. The dielectric constant for solid electrolyte polymer membranes of chitosan/PEG4000, and chitosan/PEG4000 with LiCF 3 SO 3 salt are 3,4 and 16,6 x 10 3 . XRD and EIS test results show that chitosan/PEG4000 polymer membrane with LiCF3SO3 salt as a surfactant can be applied as an alternative to solid electrolyte polymer secondary batteries.