Thin films of Li[Ni0.5Co0.2Mn0.3]O2 (NCM-523) were deposited on Au coated Si substrate by RF co-sputtering. The component ratio of Ni : [Co+ Mn] at the surface of NCM was modified through changing the power densities of each targets during deposition process. With decreasing the Ni content, a more stable surface structure of NCM has been obtained. After the all-solid-state thin film batteries with a structure of "Si/Au/NCM/LiPON/Li/Au" has been fabricated, and the electrochemical impedance spectroscopy (EIS) was taken to compare the interface resistance of "NCM/Li" with different Ni content. Systematic relationship between surface Ni content and interface resistance was established. Batteries with lower surface Ni content was with better cycle properties, showing capacity above 60 μAh*cm^-2 *μm^-1 under 0.5 C.