Microwave-absorbing structures are increasingly vital for applications such as electromagnetic protection, stealth technology, and wireless communications. However, their broader adoption is often limited by drawbacks such as excessive thickness, narrow absorption bandwidth, and high manufacturing costs. This study presents the design, fabrication, and evaluation of a sunflower-inspired metastructure for broadband microwave absorption, achieved via fused deposition modeling three-dimensional printing. The metastructure, inspired by the spiral geometry of sunflower seed arrangements, integrates multi-layered, gradient spiral elements composed of carbon black-carbonyl iron powder/polylactic acid (CB-CIP/PLA) composites. Electromagnetic simulations were employed to systematically optimize key structural parameters, including the gradient impedance increment and individual layer thicknesses, to maximize absorption efficiency. Both simulated and experimental results demonstrate that the absorber achieves an effective absorption bandwidth of 12.13 GHz (5.87 – 18.00 GHz) with reflection loss below 10 dB, covering the C, X, and Ku frequency bands. The performance is attributed to the synergistic effects of interfacial polarization and natural magnetic resonance within the CB-CIP/PLA composite. The metastructure also exhibits stable, wide-angle absorption properties, maintaining bandwidths exceeding 10 GHz for incident angles up to 50° under both transverse electric and transverse magnetic polarizations. The proposed sunflower-inspired design demonstrates significant advantages in bandwidth-to-thickness ratio, fabrication efficiency, and polarization insensitivity compared to conventional biomimetic absorbers. These findings highlight the promise of bio-inspired design strategies for developing lightweight, efficient, broadband microwave absorbers, providing valuable reference for future advancements in the field.