Silicon is a promising anode material for high-performance Li-ion batteries, but the high capacity of silicon is mainly restrained by its large volume change upon electrochemical cycling. Herein, flexible nanocomposite films of polyurethane/copper/silicon were facilely fabricated by an improved layer-by-layer self-assembly method. This method can not only avoid the particle agglomeration in the nanocomposites, but also effectively combine the typical property advantages of the three building blocks-Li storage capability of silicon, electro-conductivity of copper, and stretchability of polyurethane. The self-organization of the copper nanoparticles into necklace-like chains and three-dimensionally conducive networks during the preparation process furtherly facilitated the electron transfer in the composite films. The multifunctional films had improved mechanical flexibility (8.2 MPa tensile strength with 125.1% strain) and electro-conductivity (8 S cm(-1)), and can be directly used as anodes for accommodating the silicon volumetric change and preserving the electrical contact upon electrochemical cycle. Thus, the nanocomposite film electrodes showed high capacity of 574 mAh g(-1) after 300 cycles at 1 C and average Coulombic efficiencies of 99.2-99.8%. This work offers an simple and effective material design way to fabricating multifunctional composite films with single-function building units for energy storage applications.