In traditional anti-jamming application of GNSS (Global Navigation Satellite System), the receiver with nulling antenna composed beam nulling at the direction of jamming arrival to suppress high power jamming by the weighted sum of several channel signals. But this approach is useless for deception jamming. In this paper, a novel method for detection on navigation deception signals is put forward. Firstly according to the principle of interferometer, the signal arrival angle in nulling antenna is measured through the phase difference among the receiving channels. Then the immutability of cross-angle for arrival direction of signals in different coordinate systems is utilized. The cross-angle matrixes for real signals and reference signals are built respectively. The norm of difference between these two matrixes is calculated to show the direction departure from real signal to the reference one. Its result can be used to detect the deception signal with abnormal direction. The simulation results show the feasibility and validity of this method. It is a new anti-deception-jamming approach for navigation receivers with nulling antenna.