We investigate a channel-interleaved photonic analog-to-digital conversion (PADC) system’s ability to work stably over a long duration with an optimal driving voltage. The influence of optimum bias point drift of a Mach–Zehnder modulator (MZM)-based photonic switch on this system was analyzed theoretically and experimentally. The feasibility of extracting feedback signals from the PADC system was derived. A high-stability channel-interleaved PADC was constructed by extracting a feedback signal from a parallel demultiplexing module to control the MZM-based photonic switch’s driving voltage. Consequently, the amplitude mismatch between the channels was limited to within 0.3 dB over 12 hours of operation.