The direction of arrival (DOA) estimation and adaptive beamforming (ABF) in Four-Dimensional (4-D) antenna arrays are presented in this paper. By using time modulation technique with appropriate time sequences, multiple beams can be obtained in the 4-D antenna arrays and each of them is located at different directions. Through the analysis of the beamspace data received by the multiple beams, the DOA and ABF can be realized in the 4-D antenna array. Simulation results of the DOA and ABF in 4-D linear array are compared to those in uniform linear array (ULA), and better performance can be obtained.