With the rapid advancement of the Internet of Things (IoT) and intelligent systems, the demand for energy-harvesting technologies in sensor networks is escalating. To address the challenges of significant feature divergence in multi-channel broadband piezoelectric energy signals and low energy extraction efficiency under weakly coupled conditions, this paper proposes a multi-channel parallel synchronized switch harvesting on inductor (MCP-SSHI) interface circuit. The circuit retains high modular scalability and structural simplicity while enabling the processing of multi-channel input voltages with arbitrary phase relationships (0-2π). In test results on processing signals from six piezoelectric energy harvesters (PEH), the MCP-SSHI circuit efficiently extracted multi-channel electrical energy, with an energy extraction efficiency of as high as 79.96%, which was 3.24 times the power gain of traditional interface circuits.