The invention discloses a preparation method of a flexible transition metal sulfide negative electrode material of a sodium ion battery. The method comprises the following steps: (1) weighing glucose,a transition metal salt and thioacetamide, adding the glucose, the transition metal salt and the thioacetamide into a mixed solvent composed of a water-soluble organic solvent and deionized water, and uniformly dispersing to obtain a solution with the mass fraction of 3-10%; (2) soaking melamine sponge in the solution obtained in the step (1), taking out the melamine sponge, and drying the melamine sponge in a drying oven for 12 hours to obtain a melamine sponge loaded transition metal complex; and (3) placing the prepared melamine sponge loaded transition metal complex in a tubular furnace,and carrying out heat treatment for 1-4 hours to obtain the flexible transition metal sulfide negative electrode material. The preparation method disclosed by the invention is simple and easy for large-scale production. The prepared flexible electrode does not need a binder, a conductive agent or a metal current collector. The prepared flexible electrode has excellent cycling stability and rate capability, and has a wide application prospect in the field of flexible devices.