Inspiring by the advantages of digital peak voltage (DPV) control and digital average current (DAC) control, the digital average voltage (DAV) control for switching DC-DC converter is proposed and investigated. Taking buck converter as an example, DAV control algorithm is analyzed in detail. In order to explore the stability of system, the z-domain transfer function is deduced, by which the critical equivalent series resistance (ESR) of output capacitor is obtained. Finally, DAV controlled, DPV controlled and DAC controlled buck converter are compared by time-domain simulation. Results indicate that DAV control possesses better steady accuracy as well as DAC control. In addition, DAV controlled buck converter is in stable state during the whole duty ratio. Moreover, DAV control and DPV control have similar load transient performance but DAV control behaves lower overshoot voltage with load variation.