Parity-time (PT) and anti-parity-time (APT) symmetries have provided important guiding principles in the researches of non-Hermitian physics. Particularly, the realization of APT symmetries in photonic systems usually relies on optical nonlinearities or indirect-coupling methods. Here, we reveal a linear, direct-coupling mechanism of introducing gauge-flux biasing into open-cavity systems to attain APT symmetries. We show that a π-flux biasing in a looped-resonator array can force a degeneracy between a pair of Bloch modes in the array. By further coupling the array to external bus waveguides, the system near the degeneracy point can be described by an APT-symmetric Hamiltonian. As gauge-flux varies, the system undergoes a spontaneous transition between APT and APT-broken phases, with which we can switch between two extreme cases of complete channel-drop tunneling and complete tunneling suppression. Moreover, by adding a PT-symmetric term onto the APT-symmetric Hamiltonian through applying an imaginary gauge-flux biasing, we also achieve extreme channel-drop amplifying effects by reaching the “lasing point” under the critical-coupling condition. Our work bridges the physical connection between synthetic gauge field and non-Hermitian APT symmetries, which may also find many applications from optical routing, switching to buffering and amplifying on a chip-scale platform.