Abstract: To address the issue of inconsistencies between the actual strength and failure mode of composite multi-row nail connection structures and traditional engineering algorithms, this study investigated nail load distribution patterns in composite connection structures based on fibre optic bolt testing techniques. The study primarily examines the effect of process characteristics such as nail load asymmetry, assembly sequence and assembly clearance on nail load distribution, while also establishing a high-precision finite element model for comparative study. The results indicate that asymmetric nail loading in a multi-row nail connection structure exacerbates uneven nail load distribution. Assembly sequence affects nail load distribution, and installing the outermost bolt last during bolt assembly can effectively reduce differences in nail load distribution. Nail load distribution in structures with uniform assembly clearance is consistent with load distribution in structures with no clearance. Additionally, the study finds that the proportion of critical bolt nail loads measured through testing is over 10% higher than the finite element results, suggesting that engineering algorithms need to be modified based on manufacturing and process characteristics such as assembly clearance.