The invention provides a preparation method of a lithium battery with a long cycle life, and the method comprises the following steps: preparing positive electrode slurry with the solid content of 60-75%, preparing negative electrode slurry with the solid content of 30-35%, preparing a high-flexibility positive electrode piece and a high-flexibility negative electrode piece, preparing a lithium battery cell from the positive electrode piece, a diaphragm and the negative electrode piece through a winding machine, packaging the lithium battery cell in a shell, and carrying out groove rolling, cap welding and liquid injection to generate the lithium battery, wherein the positive electrode solid material comprises the following components: 0.4-2.1 parts of PVDF, 0.3-1.8 parts of a first conductive agent and 80-98 parts of a second conductive agent; the negative electrode solid material comprises the following components by weight: 1-2.8 parts of a thickening agent CMC, 0.1-1.5 parts of a second conductive agent, 80-97 parts of a negative electrode material and 1-3.5 parts of a binder SBR. A long-range conductive first conductive grid is formed in the positive electrode piece, and a long-range conductive second conductive grid is formed in the negative electrode piece. The preparation method provided by the invention can improve the cycle performance and the capacity performance ofthe lithium battery.