Abstract: Since 2022, Zhangjiaheba Gully in Baohua Township, Jiuzhaigou County, Sichuan Province, has experienced over 10 debris flow disasters of varying scales. On July 24, 2024, the gully was once again hit by a debris flow, causing significant damage to local residents, roads, and infrastructure. The development of loess landslides within the watershed is the primary factor contributing to the frequent occurrences of debris flows. The “7•24” landslide-debris flow disaster chain in Zhangjiaheba Gully was investigated through field surveys, hydrological model calculations, seismic model calculations, and rainfall analysis across varying timescales. The research findings reveal that the “7•24” landslide-debris flow in Zhangjiaheba Gully has a bulk density of 2.116 g/cm³, classifying it as a viscous debris flow with an average flow velocity of 4.87 m/s and an average impact pressure of 5.29 Kpa. Its disaster-causing mechanism is attributed to the combined effects of earthquakes and rainfall. The peak ground acceleration of the 7.0-magnitude Jiuzhaigou earthquake at the Zhangjiaheba Gully reached 183.11 cm/s², far exceeding the critical acceleration of 98 cm/s², causing permanent damage to the landslide, loosening its structure, and increasing its susceptibility to failure. The triggering rainfall threshold for debris flow in the Zhangjiaheba Gully was 13.52 mm. On July 24th, the daily rainfall reached 45.8 mm, significantly exceeding the threshold, which initiated the formation of the landslide-debris flow disaster chain. The evolution process of this disaster chain follows a pattern of earthquake-rainfall-landslide-debris flow-reciprocal regeneration, with the chain formation process primarily driven by strong earthquakes and rainfall. Influenced by rainfall, continuous loess landslides in Zhangjiaheba Gully result in the reciprocal regeneration of debris flows and landslides within the watershed. These research outcomes provide a reliable scientific basis for the engineering management and disaster prevention and mitigation of the landslide-debris flow disaster chain in Zhangjiaheba Gully.