Impedance matching is the premise of obtaining a perfect absorbing effect. Through improving the impedance matching condition of the grid-structured absorber by covering a layer of 0.5mm thick 3D printed disk structure. The bandwidth of the new structure with the reflection loss less than -10dB is optimized from 5.3-10.2GHz and 14.8-18GHz to 5.3-18GHz. And the total thickness is 3.5mm. The experimental results further validated the simulation results. The broadband absorption attributes to the synergistic effect of the dielectric loss and magnetic loss. Additionally, the optimized impedance matching is the critical precondition. Due to the 3D printing technology, the printing layer all-dielectric structure can be flexiblly fabricated. The tailored strategy of optimizing the impedance matching by the 3D printed all-dielectric plays a guiding role in the realization of broadband absorption.