The invention provides a high-voltage and high-volumetric-energy-density long-life lithium ion battery and a preparation method thereof. The battery comprises a lithium ion battery outer shell aluminum-plastic packaging film, a positive electrode piece, a negative electrode piece, an isolation film, an electrolyte, and positive and negative electrode lugs, wherein the positive electrode piece uses carbon nanotubes (CNTs) as a conductive agent, and the isolation film comprises a polyolefin isolation film base and a mixed coating of Al2O3 and polyvinylidene fluoride (PVDF); the surface of the polyolefin isolation film base is coated with the mixture of Al2O3 and polyvinylidene fluoride (PVDF). The high-voltage and high-volumetric-energy-density long-life lithium ion battery provided by the invention not only has volumetric energy density of greater than or equal to 700Wh / L, but also has good electrochemical performance and safety performance, has outstanding cycle performance, and has a cycle life of 800 times and a capacity retention rate of 80% or above at normal temperature.