Abstract: Combined with a 500 kV transmission line capacity expansion and reconstruction project in Guangdong, this paper makes a comprehensive comparison and analysis of commonly used capacity expansion conductors. Through the analysis and comparison of the current carrying capacity, sag characteristics and economy of the four kinds of capacity increasing conductors. When the capacity increase reaches 50% in the 500 kV line project, the current carrying capacity and sag of aluminum-clad steel core heat-resistant aluminum alloy stranded wire can meet the requirements of line capacity increase, and the economic benefit is optimal.