The invention discloses a piezoelectric energy collection system and a control method thereof. The piezoelectric energy collection system comprises a piezoelectric energy collector, an active rectifier, a Buck-boost converter, an asynchronous control circuit, a self-startup precharge circuit, a peak detection circuit, an inductance input-end voltage zero-crossing detection circuit, a VDD-end energy storage unit, a charge current zero-crossing detection circuit of the VDD-end energy storage unit, a VST-end energy storage unit, a charge current zero-crossing detection circuit of the VST-end energy storage unit, an inter-storage-unit energy conversion circuit, an LDO voltage-stabilizing circuit, a VDD internal voltage-stabilizing circuit and a low-power reference current source and reference voltage generation circuit. According to the invention, an ultralow-power design technology is introduced, a conventional circuit structure is improved, performance optimization and structural innovation are performed on each circuit module, static power consumption of the whole circuit system is reduced to 111.1nW, and the energy conversion efficiency is as high as 89.4%. Besides, the system also has the advantages of small chip area, high integration, complete automation, high adaptive capacity to environment and the like.