For aluminum joints with a stacking thickness exceeding 6.0 mm, traditional self-piercing riveting may not achieve satisfactory joint quality and can lead to uneven stacking surfaces. In this paper, an engineering optimization process flat-stacking-surface (FS-SPR) is proposed to address these issues by reducing the stacking thickness. To ensure joint quality, the effects of riveting distance, overlap distance, and overlap surface type on the mechanical properties, and failure behaviors of the FS-SPR joints are investigated in this paper. Moreover, the quasi-static and fatigue properties of FS-SPR joints are systematically assessed. Specifically, the Weibull distribution is employed to predict the fatigue life of FS-SPR joints. The results indicate that the undercut values on the right side of FS-SPR joints with inclined overlap surfaces are consistently larger than those on the left side, and they gradually decrease with an increase in riveting distance. Among all FS-SPR joints with inclined overlap surfaces, the 40–20 joint exhibits the best mechanical properties. Compared to the 40–30 joint, the peak force and energy absorption of the 40–20 joint are 3.54 times and 8.74 times higher, respectively. The peak force of the 40-20-F joint is 13.5 % higher than that of the 40–20 joint, while the energy absorption is 18.4 % lower. The fatigue life of FS-SPR joints with flat overlap surface is at least 2.03 times higher than that of inclined overlap surfaces. Compared to smaller overlap distances, FS-SPR joint with larger overlap distance has a fatigue life that is 4.48 times higher.