The invention belongs to the technical field of electronic information, and relates to a passive interferometer attitude determination method, according to the method, attitude determination of a movement platform is conducted according to phase differences between radiation source signals, measured at different moments, of an interferometer, the interferometer only needs two antennas, and the attitude of the movement platform can be determined when there is only one radiation source in the environment and the position of the radiation source is unknown, so that compared with common platform attitude determination methods, the passive interferometer attitude determination method has the advantages that the cost and the system complexity of platform altitude measurement are reduced and highpracticality in the real environment is realized.