The non-destructive testing (NDT) effectiveness of aircraft honeycomb sandwich structures is directly influenced by the condition of test specimen. However, defects introduced during the manufacturing of these test specimens can distort test results for actual components, potentially compromising aircraft operational safety. To address this critical technical challenge, this study focuses on the design, process optimization, and analytical methods of NDT test specimens. An innovative approach integrating self-developed liquid cover plates and PMI foam end-seals has been proposed to enhance testing accuracy. Based on the theoretical analysis of slope curvature in wedge-shaped honeycomb cores and cell size dimensions, a 15% attenuation value was identified between detected defect areas and actual embedded defects. To address this discrepancy, an area compensation algorithm was developed to ensure that detected defect sizes align with flaw detection requirements. Furthermore, through systematic research using reflection method A-scan and transmission method C-scan techniques, the design and manufacturing process of ultrasonic testing specimens for wedge-shaped aramid paper honeycomb-carbon fiber sandwich composite structures were systematically established. The detectability of various internal defects in these structures was experimentally analyzed and compared. Practical verification demonstrates that this optimized reference block significantly enhances interlaminar damage detection efficiency to 97%, reduces vertical linear error to ≤2.3% and horizontal linear error to ≤0.1%. This advancement not only improves testing accuracy and reliability but also provides a robust technical foundation for NDT of wedge-shaped honeycomb composite components in aircraft manufacturing, ultimately contributing to enhanced quality control in aircraft production.