The invention discloses a debris flow sediment transport control method suitable for a broad valley type debris flow gully. The transverse width of the broad valley type debris flow gully is 50-400 m, and the longitudinal gradient of a gully bed is smaller than or equal to 15 degrees; a sediment transport groove in the gully bed is backfilled by utilizing existing loose solid materials on the gully bed in the flowing area and accumulation area of debris flow in the gully, and the ground line curvature of the backfilled groove is smaller than three percents; multiple sand blocking cob walls distributed at a certain interval are transversely built by utilizing the existing loose solid materials on the gully along the gully contour line in the flowing area and accumulation area of the debris flow in the gully; deep-rootedness arbores or bamboos are planted at the edges of the cob walls along the trend of the cob walls in the shape of a strip. According to the method, not only is sediment effectively prevented from entering a main river, but also a large amount of the blocked sediment can be locally converted into precious land resources, and the comprehensive corporate governance goals of achieving low governance cost and high economic benefit, changing harm to benefit and improving the ecology landscape of the gully are achieved.