Abstract: The principle of using three satellites formation to reconnoiter and surveil targets on ocean passively is analyzed. The precision model of location making use of measuring the time difference of arriving is built. Based on the precision model, the relation between location precision and the satelliters′ formation configuration, orbit height, relative position with targets, orbit determination precision and measure error are deduced. The results of simulation show that increasing baseline length between the satellites rationally and maintaining uniformity of the satellites formation configuration and their relative position with target can improve the precision of locating target effectively.