Purpose <p>This study proposes gradient stacked piezoelectric (PZT) phononic crystals based on asymmetrically arranged and uniformly stacked PZT phononic crystals. Accordingly, a design strategy for the shunting circuit parameters is proposed to achieve broadband vibration attenuation with stable performance and a wide frequency range.</p> Methods <p>The bandgap coupling mechanism and damping characteristics of the asymmetrically arranged PZT phononic crystals are verified by simulations and experiments under the appropriate shunting circuit parameters. The bandgap coupling mechanisms of the uniformly stacked and the gradient stacked PZT phononic crystals are investigated by combining equivalent stiffness analysis with complex band structures. The design strategy for shunting circuit parameters corresponding to the broadband vibration reduction of the two structures is developed.</p> Results and Conclusions <p>Simulations demonstrate that applying the shunting circuit strategy to gradient stacked PZT phononic crystals yields stable, broadband vibration attenuation, with a specific parameter configuration achieving a broad bandgap of 164&#xa0;Hz. Modulating the inter-layer inductance difference can balance the bandwidth and attenuation factor. Experimentally, asymmetric PZT configurations with distinct surface circuits extend the bandgap and enhance damping. Additionally, increasing resistance in the low-frequency resonant circuit effectively improves attenuation within the transition regions. Ultimately, this work provides a novel approach for multi-modal and broadband vibration reduction.</p>