As the weak ambient energy is hard to be stored directly and rapidly and unable to drive the electronic load into working properly, a high-efficiency energy storage circuit, with quartz crystal serving as a storage element, is presented. When an alternating electric field is applied to it, the quartz crystal will generate mechanical oscillations of a certain frequency. Since the quartz crystal possesses a high quality factor, in the piezoelectric crystal plate there appears a severe mechanical resonance with a small excitation voltage. In the resonant condition, the external weak electrical energy can be converted into mechanical energy stored in the quartz crystal. The principles of quartz crystal energy storage and instantaneous energy discharge are theoretically analyzed. The relationships between the output voltage and the time and between the maximum instantaneous output power and the load in the processes of quartz crystal charging and discharging are deduced, respectively. The storage characteristics of the quartz crystal are investigated experimentally. The experimental results show a good accordance with the theoretical analysis. A quartz crystal of 1 MHz resonant frequency is adopted in this research. When the input voltage amplitude of the energy storage circuit is 100 mV, the optimal matching load is 820 and the maximum instantaneous output power of quartz crystal discharging circuit is 150 W. The storage efficiency and the release efficiency of the quartz crystal can reach up to 77% and 71.4% respectively. These results provide evidence for quartz crystal energy storage in the condition of weak ambient energy.