The effect of head rotation on median plane sound source (or image) localization is studied. It is suggested that, at low frequency, the change of interaural time difference (ITD) caused by head rotation supplies information for determining sound source direction in the median plane. Based on the suggestion, the summed sound image localization equations for multiple loudspeakers arranged in the median plane are derived. Especially, for a pair of loudspeakers arranged front-back symmetrically in the median plane, the localization equations are similar to that of stereophonic sound in horizontal plane. A sound image localization experiment was carried out to prove the theoretical analysis. The results of this paper are not only available to virtual spatial auditory, but also supply a quantitative validation of the hypothesis that head rotation is a cue for sound source localization in the median plane at low frequency. The effect of head rotation on median plane sound source (or image) localization is studied. It is suggested that, at low frequency, the change of interaural time difference (ITD) caused by head rotation supplies information for determining sound source direction in the median plane. Based on the suggestion, the summed sound image localization equations for multiple loudspeakers arranged in the median plane are derived. Specifically, for a pair of loudspeakers arranged front-back symmetrically in the median plane, the localization equations are similar to that of stereophonic sound in horizontal plane. A sound image localization experiment was carried out to prove the theoretical analysis. The results of this paper are not only available to virtual spatial auditory, but also supply a quantitative validation of the hypothesis that head rotation is a cue for sound source localization in the median plane at low frequency.