We propose a depth-averaged current estimation method. Firstly, based on a stable motion model of an underwater glider, we discuss the influence of seawater density difference and compression deformation of pressure hull on the movement of the glider. We then build a rapid-calculation model for glider speed, and demonstrate its effectiveness and feasibility. In combination with recalculated glider speed and dead reckoning, we present a depth-averaged current estimation method. We estimate the depth-averaged currents from the sea trials of three different gliders using this method, and demonstrate its effectiveness. The results show that the accuracy of dead reckoning positioning of underwater gliders can be improved with the help of depth-averaged currents.