Aiming at the isolation of low-frequency sound, a kind of thin-film acoustic metamaterialis designed and obtained by implanting PZT into thin film. The finite element method (FEM) of the structure is built, and 1^st–14^th order eigenfrequencies and transmission loss between 20–1200 Hz are calculated. The reliability of finite element calculation is verified experimentally and the existence of adjustable sound insulation peak is monitored in the experiment. The results show that the acoustic metamaterial has good sound insulation performance in a frequency range between 20 and 1200 Hz, and has two sound insulation peaks of more than 50 dB, and there is a sound insulation peak which can be changed by adjusting the parameters of the outer circuit. By analyzing the first resonance mode of simple structure and building its equivalent model, the effect of structural parameter on the sound insulation performance of thin film acoustic metamaterial is investigated theoretically, and the rationality of the equivalent model is verified by the finite element calculation. The sound insulation mechanism of the structure is further illustrated by taking into consideration the eigenfrequencies, transmission loss curve and vibration mode diagrams at various frequencies. It is found that at the resonance frequency, the flapping motion of the film will cause the sound wave in the subsequent propagation to cancell the interference, therefore realizing the attenuation of the sound wave. Based on Fano resonance theory, the reasons for the different characteristics of transmission loss curves at different resonance points are investigated. The PZT and outer circuit can form a LC oscillator. At the resonant frequency of the oscillator, the vibration of the piezoelectric material can absorb the energy of sound wave to cause a sound insolation peak. The resonant frequency of the circuit can be adjusted by changing the parameters of the outer circuit, thereby realizing the adjustability of the sound insulation performance. The influence of eccentricity of piezoelectric mass block on sound insulation performance of material is explored, proving that the sound insulation performance can be further optimized by improving structure. And through the finite element calculation, it is proved that the sound insulation performance of material is adjustable by changing the parameters of the outer circuit. The results provide a theoretical reference for designing the thin film acoustic metamaterials.