A carbon material-polymer strain sensitive film and its preparation method are disclosed. The carbon material-polymer strain sensitive film includes multiple layers of carbon sensitive films and multiple layers of polymer films, wherein the multiple layers of carbon sensitive films and the multiple layers of polymer films form a multi-layer composite film in sequence through a layer-by-layer assembly process. The preparation method includes steps of: cleaning, processing a hydrophilic treatment and processing a hydrophobic treatment on a rigid substrate in sequence; preparing a carbon material in dispersion solution and a polymer dispersion solution; through a layer-by-layer self-assembly process, growing the polymer and the carbon material in a form of layer-by-layer on the rigid substrate; transferring the composite film from the rigid substrate to a flexible substrate; and pasting two electrodes at two ends of the composite film and encapsulating with a flexible film.