The localization principle and error source of DV-Hop algorithm which is classic self-localization algorithm in wireless network are introduced in this paper. Aiming at the disadvantage of DV-Hop algorithm on localization accuracy, an improved scheme by modifying the average hop distance is proposed. The simulation results show that the comprehensive properties of the improved algorithm (including the localization accuracy, communication expenses, computational complexity and hardware facilities, etc) have obvious advantages compared to the basic DV-Hop algorithm. It improves node localization accuracy largely by paying little price.