This paper presents a piezoelectric energy harvesting (PEH) interface circuit, which integrates an adaptive synchronized switch harvesting on inductor (SSHI) circuit and an active rectifier. The proposed adaptive SSHI circuit utilizes the signal of the active rectifier to control the synchronized switch so that the external control is not needed and the proposed PEH circuit can be effective for varies inductance. The active rectifier circuit and the switch control circuit of this paper are directly powered by the storage capacitor, which avoids the auxiliary power supply. As a result, the PEH interface circuit is self-powered. The proposed circuit has been designed in 0.18-μm CMOS technology, and the simulated power consumption of the control part is 0.178 μ W. The simulation result shows the output power is 4.6 times of that in the ideal full-bridge rectifier. Moreover, without any external power supply, it is capable of cold startup to provide a stable output voltage.