The invention belongs to the fields of electric power system energy storage optimization and new energy energy-storage optimization, and relates to an over-charging and over-discharging protection apparatus-equipped mixed energy storage power distribution system and method having a variable time constant. The system comprises a mixed energy storage power distribution module with a variable time constant controller, a state of charge-based mixed energy storage over-charging and over-discharging protection apparatus, a storage battery energy storage module, a supercapacitor energy storage module, a photovoltaic power generation module and a direct current load. By virtue of the mixed energy storage power distribution system and method, the storage battery power high fluctuation can be lowered effectively, and the service life can be prolonged; and meanwhile, operation of the system in the fault direction can be avoided according to a power instruction and an energy storage element statematching degree over-charging and over-discharging protection strategy, so that risk of accidents can be lowered.