This study investigates the four-wave mixing (FWM) processes from two channels in an inverted Y-type four-level atomic system driven by a periodic phase-modulation field using the density matrix equation. The numerical analysis results denote that the FWM signals from the two channels can be controlled to overlap or separate by the probe field with periodic phase modulation. The suppression, enhancement, and splitting of the FWM signals can be observed by selecting different modulation frequencies, modulation coefficients, and dressing field strengths. This FWM control with a periodically driven field can be probably used in the optimization of optical nonlinear processes and the optical information processing.