To address the failures observed in aluminum-alloy fuel tanks, specifically, cracking of the dual-chamber sealing partition, end cover, and drain boss, finite element analysis was employed for comprehensive calculation and structural optimization. Stress, strain, and displacement under varying load conditions were evaluated, revealing that failures of the sealing partition and end cover were due to stress concentration. At the same time, the cracks in the drain boss were caused by weaknesses in the weld heat-affected zone. Three optimization measures were proposed: adding an R5 chamfer to sealing baffles, incorporating R5 transitional fillets on the reinforcing ribs of the end caps, and designing the drain boss as an asymmetrical elliptical shape with a central transitional fillet. Following these optimizations, the maximum stress on the components was significantly reduced, and the safety factor markedly increased. Results from sealing, pressure, and vibration tests confirmed that these measures effectively enhance the structural strength of aluminum-alloy fuel tanks and extend their service life. This study provides robust support for the design and analysis of aluminumalloy fuel tanks.