In order to solve the problem that the energy density of supercapacitors is small and the state of charge(SOC) is easy to exceed the limit during operation, this paper improves the traditional low-pass filtering method and proposes a power allocation strategy considering the SOC of supercapacitors. The method divides five different working areas according to the supercapacitor SOC, and takes the supercapacitor SOC as the variable, establishes the corresponding functional relationship with the filter time constant in the different working areas, and then dynamically adjusts the filter time constant according to the SOC change, so as to realize the reasonable distribution of power between the battery and the supercapacitor, and ensure that the supercapacitor SOC is maintained in a reasonable range. Finally, the relevant model is built in Matlab/Simulink and the correctness and effectiveness of the proposed scheme is verified by simulation. The simulation results show that, compared with the traditional low-pass filtering method, this method can reasonably allocate the power demand of the supercapacitor and the battery according to the supercapacitor SOC while stabilizing the power fluctuation, so that the supercapacitor SOC can recover itself, prevent its overcharge and over discharge, and improve the economy and stability of the DC microgrid system operation.