The invention discloses a lithium battery diaphragm with a toughened and modified polyvinylidene fluoride base body and a preparation method of the lithium battery diaphragm. The preparation method of the lithium battery diaphragm includes the following steps of (1), preparation of a polyvinylidene fluoride (PVDF)-acrylic ester rubber (ACM) solution; (2), preparation of modified nano silica; (3), preparation of a polyvinylidene fluoride-modified nano silica hybrid solution; (4), membrane spraying and drying and membrane forming; (5), membrane hot-pressing processing. According to the lithium battery diaphragm with the toughened and modified polyvinylidene fluoride base body and the preparation method of the lithium battery diaphragm, the acrylic rubber (ACM) is adopted to modify the polyvinylidene fluoride (PVDF) so as to improve toughness of the polyvinylidene fluoride, so that the breakage rate in the production process is lowered, and the service life is prolonged; meanwhile, the surface energy of the PVDF membrane is improved, lithium battery electrolyte can better moisten the membrane, and performance of batteries is improved.