Abstract: As a critical energy equipment in industry, the welding quality of alloy steel small-diameter pipes (used in water-cooled wall tube panels and high-temperature superheater tube panels) in boilers is paramount. During the manufacturing of boiler water-cooled wall tube panels and superheater tube panels, fixed-position butt welding is required for tube connections. Welding in fixed positions poses significant operational challenges, often leading to root pass cracks. Metallographic testing confirmed that these root pass cracks are hot cracks. Hot cracks in boiler tube butt welds under high-temperature and high-pressure conditions are highly hazardous, making it essential to develop a solution for mitigating circumferential weld hot cracks. Through root cause analysis and simulated experiments, key factors contributing to root pass cracks were identified. Measures implemented in welding techniques and critical node control effectively improved welding qualification rates, which is crucial for ensuring the safe and stable operation of boilers.