Abstract: The characteristics of azimuth scattering signal in tropospheric passive direction finding system is researched. By defining the power factor of tropospheric scattering azimuth and analyzing the effects that different parameters make on the factors, the relationship between the received signal power median value and receiving antenna azimuth beam width was obtained. Focusing on the orientation precision and orientation fuzzy problems during the measurement of the target, we found it existed the minimum direction finding error and minimum fuzzy angle independent from the antenna, then analyzed the reasons of these problems, and derived to the relationship between the minimum direction finding error or minimum fuzzy angle, and target antenna or distance, etc.