To analyze the spatial distribution of aluminum stress in long-span overhead transmission line, this study focused on the JLHA1/G6A-500/280 ultra strong steel cored aluminum alloy conductor. A stress test platform for aluminum in long-span conductors was established using laser grooving on the aluminum strand and embedding ultra weak fiber gratings known for their high sensitivity and super multiplexing capacity. The research investigated the aluminum stress distribution in the long-span overhead transmission conductor under various tension conditions. A finite element model of the long-span conductor was created, and the stress distribution characteristics of the aluminum strand was analyzed, with the test results validated against the model. The results show that under tension, the stress in the outer aluminum strand differs from that in the sub outer aluminum strand, with the outer aluminum strand experiencing lower stress. The stress within the same layer of the conductor remains consistent. The aluminum strand stress increases linearly with the increase of conductor tension, with a roughly 10% increase in aluminum strand stress for every 1% increase in tension. Under different conductor tensions, both steel and aluminum strands show ring delamination characteristics. The average stress in the aluminum strand is less than that in the steel strand, with a stress ratio of approximately 3∶7 between aluminum and steel strands. Additionally, the stress distribution of the aluminum alloy strand in the outer layer and sub outer layer is uneven along the circumferential direction. This study suggests considering the delamination characteristics of the aluminum strand in the linear design of long-span conductors.