Abstract: Data fusion is one of the attractive topic in sonar signal processing. Decision level data fusion of Multi- sensor (multi-array) system is described in this paper. Follow the discussion in literature¹, the optimum linear data fusion algorithm for N dependent observations is derived. it is proved that the estimation error of data fusion is not greater than that of individual components. The expression of estimation error and weight coefficients are presented. The results of numerical calculation and some examples are illustrated. The effect of dependence of observation data for the final estimation error is presented.