Disclosed in the present invention are a method for synthesizing a high-safety positive electrode material by recycling positive electrode leftover materials, and an application. The method comprises: adding an acid and a reducing agent into positive electrode leftover materials for dissolving, carrying out solid-liquid separation to obtain a first filtrate, adding an alkali into the first filtrate to adjust the pH value for reaction for a period of time, so that most of aluminum ions are precipitated, carrying out solid-liquid separation to obtain a second filtrate, carrying out precipitation reaction on the second filtrate to obtain a precursor, mixing the precursor, a lithium salt and a fluorine source, and calcining in an oxygen atmosphere to obtain a high-safety positive electrode material, wherein the fluorine source is PVDF. According to the present invention, a high-performance and high-safety Al and F co-doped positive electrode material is synthesized by recycling waste positive electrode leftover materials; by means of the synergistic effect of A1 and F, the structural stability of the material at a high temperature is improved, structural damage caused by reaction between the positive electrode and the electrolyte at a high temperature is effectively inhibited, the safety is improved, cation mixing is reduced, ion migration kinetics of lithium ion deintercalation and intercalation are enhanced, and excellent electrochemical performance is achieved.