In DC microgrids, the bus voltage is an important control signal for the existing power management strategies since it is a common signal for all distributed units, which, however, requires remote measurement and transmission. The most alternative implementation of using local terminal voltage for control instead of the bus voltage is not able to always ensure all the distributed units in the system operate in the appropriate operating mode when considering line resistances. Focusing on the challenge, a small-AC-signal (SACS)-injection-based coordinated control method is proposed in this paper, where an estimated bus voltage that is extremely close to the actual bus voltage is used as the control signal. Each distributed unit estimates the bus voltage utilizing local voltage and current information as well as a roughly estimated line resistance, and the difference among the estimations are always suppressed to zero based on the injected SACS. Firstly, the proposed coordinated control method is explained in detail. Then, the comprehensive design procedure for control parameters is provided via steady-state and dynamic analysis of the system. Finally, simulation and experiment results demonstrate the effectiveness of the proposed control method.