DC (Direct Current) microgrid has gained more attention caused by the development of distributed generations and DC loads. The control objectives for DC microgrid are voltage regulation and current sharing. In order to achieve these objectives, consensus based control methods with communication have been extensively studied recently. It is a common strategy to modify the voltage set point of local controller according to the average voltage and current in the system. However, there are some limitations for this method, such as specific communication structure and scalability limitation. This paper proposes an improved cooperative control method. The structure of local controller is simplified and one voltage correction item is generated by the cooperative controller to adjust the reference voltage for local controller. In addition, a novel method in calculating the average voltage and current difference of the multi-node system is applied to reduce the effect of communication delay and increase the scalability. Finally, a four-converter system with ring communication structure is simulated based on Matlab/Simulink to verify the performance of control method.