This patent proposes the method which can enhance the accuracy in ultrasound diagnosis with low hardware complexity cost by improving dynamic focusing delay calculating precision with reduced number of delay calculator. This method comprises of 4 steps: collecting timely-seperated three delays (i.e., P1, P2, and P3) into registers for a channel, deriving two different slopes between them (i.e., S1: P1~P2 and S2: P1~ P3), interpolating dynamic focusing delays between P1 and P2 by adaptively synthesizing two different slopes (S1 vs. S2).