The control objective of DC microgrid is to ensure the accuracy of current distribution and reduce the deviation of DC bus voltage, so as to maintain the power balance of the system. These two control objectives cannot be achieved simultaneously by the traditional droop control. By using the distributed secondary control framework, this paper proposes an improved control strategy for DC microgrid based on discrete time interaction, including continuous-voltage control and discrete-current control, which can ensure the accuracy of current distribution and reduce the voltage deviation of DC bus simultaneously. Different from other proposed control methods, the proposed method in this paper only needs to sample the average current information at discrete times, which reduces the communication burden. The system model is built in MATLAB/Simulink to verify the effectiveness of the proposed control strategy.