Abstract: The direction finding (DF) method based on multi-beam array has the advantage of high accuracy. However, each beam needs an independent radio frequency (RF) channel, which leads to the complexity and high cost of the DF system. The inconsistencies of amplitude and phase between channels will also increase the DF error. A full-angle DF method with a single RF channel based on time modulated multi-beam array is proposed in this paper. The multi-beam array DF system is simplified into a single RF channel system by time modulation. The harmonic characteristic is utilized to calculate the received signal amplitude of each beam to obtain the direction of the arrived signal with high precision, and the complexity and cost of the system are reduced. The simulated results show that the proposed method achieves less error than the multi-channel DF method based on the multi-beam array under same conditions. The measured results show that the DF error of the proposed method is less than 1.3° operating from 4 to 5 GHz, which is smaller than that of the existing multi-beam arrays.