A two-dimensional direction finding ambiguity resolution algorithm about millimeter wave interferometer is proposed in the paper. By means of implementing one or more times virtual transformation operation on measured phase differences between the original circular array elements and the reference array element, the unambiguous phase differences between the virtual array element and reference array element are achieved. The unambiguous phase differences are used to give rough but unambiguous estimation of direction of arrival (DOA), which are used as coarse references to disambiguate the cyclic phase ambiguities in phase differences between the original array element and the reference array element. The high-precision estimations of DOA are acquired. Simulation examples have verified that the algorithm can obtain the two-dimensional direction finding results with high accuracy in the millimeter wave frequency range.