The present application discloses a positive electrode plate, a preparation method thereof, and a lithium-ion secondary battery, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film includes a positive active material which is a lithium manganese-based positive active material; and wherein the volume resistivity ρsum of the positive electrode plate, the powder volume resistivity ρ of the positive active material under a pressure of 20 MPa and the mass percentage a of the positive active material in the positive electrode film satisfy ρsum/ρ97.5-a≤3. The positive electrode plate provided in the present application enables the lithium-ion secondary battery to simultaneously have higher safety performance, rate performance and cycle performance.