An active phased array antenna system with hierarchical modularized architecture is introduced, which includes an array antenna and a beamforming circuit. The array antenna includes a plurality of antenna units, number of which is N and which are arranged in array form. The beamforming circuit is for receiving a plurality of input signals and a plurality of phase control signals, and includes a hierarchical circuit structure based on phase shifters, for outputting a plurality of output signals based on the input signals according to phase values corresponding to the phase control signals and combinations of the phase values; the output signals are respectively coupled to the antenna units so as to generate a radiation pattern, wherein number of the phase control signals is T, T