Mass transport deposits (MTDs) are crucial components of deepwater sedimentary systems, playing a significant role in resource exploration and geological hazard assessment. Gas hydrate drilling in the Qiongdongnan basin has revealed three distinct MTD sets above the gas hydrate layer. However, limited research on the sedimentary characteristics and controlling factors of these MTDs hinders our understanding of their influence on the underlying gas hydrate reservoir. This study focuses on the third MTD set (MTD3), situated directly above the gas hydrate layer. By comprehensively using 2D/3D seismic data, logging data, and core samples, we investigated the sedimentary characteristics of MTD3, explored its sediment source, and analyzed the controlling factors influencing its formation and its impact on the underlying gas hydrate reservoir. Our results indicate that MTD3 mainly consists of muddy sediment exhibiting pronounced deformation features. Logging data reveals low gamma ray values, low resistivity values, and irregular imaging characteristics,whereas seismic profiles show chaotic or blank reflections. MTD3 comprises of two structural units: a body slip area and a toe extrusion area, lacking a head stretching area. It exhibits a stripshaped distribution, covering an approximate area of 3600 km2. Sediment provenance analysis suggests that the sediments originated from the northwestern continental slope of the Qiongdongnan basin and were transported SW to NE in the central depression. The development of MTD3 is attributed to a complex interplay of factors, including seabed topography, tectonic and seismic activity, sedimentation rates, and sealevel changes. The toe extrusion zone of MTD3, in conjunction with hemipelagic sediments, forms a cap layer. The tight lithology and shallow overpressure within this cap layer may contribute to the accumulation of gas hydrates. This study enhances our understanding of Quaternary shallow event deposits in the Qiongdongnan basin and provides valuable geological insights for predicting gas hydrate resources related to MTDs.