The complex longitudinal dunes in the Kumtagh Desert have sparked divergent views regarding their formation mechanisms, particularly under traditional bimodal wind models, with limited exploration of their morphodynamic maintenance. In this study, we integrate satellite-derived dune morphology, sedimentology, and aeolian dynamics to reveal the formation and morphodynamic maintenance mechanisms. Sediment availability is severely limited, exhibiting a bimodal distribution (D-10 = 114.1 mu m, D-50 = 227.2 mu m, D-90 = 666.7 mu m) with a sorting coefficient of 1.02 (moderately to poorly sorted), indicating hybrid transport through both fluvial and aeolian processes. The morphodynamic maintenance of these dunes is governed by an asymmetrical tridirectional wind regime and stabilized by the feedback of sediment grain-size sorting. The region is characterized by a high-energy wind environment (drift potential = 520.17 VU, > 400 VU), comprising a prevailing north-northeasterly wind (44.62%, 8-10 m/s), followed by secondary easterly (33.56%) and westerly (20.79%) winds. Under this regime, the resultant transport vector of the NNE and easterly winds drives the longitudinal elongation of the primary ridge. Concurrently, the net transverse sediment transport driven by the easterly wind creates a profound topographic asymmetry, sculpting the secondary barchans as it reattaches to the northwest flank. Conversely, the westerly airflow, blowing anti-parallel to the secondary crestlines, avoids transversally destroying these crescentic structures. As it crosses the primary crest, it experiences intense flow separation and longitudinal deflection, sweeping the steep southeast slip face to preserve the striking one-sided superimposition. Furthermore, this asymmetrical aerodynamic forcing induces intense aeolian sorting: coarse sand lags on the lower stoss slopes to stabilize the primary ridge, while mobile fine sand is transported over the primary crest and deposited by the reattached easterly airflow to supply the active secondary barchans. Ultimately, these findings highlight the coupled effects of an asymmetrical tri-directional wind regime, topographic-aerodynamic feedbacks, limited sediment supply, and spatial grain-size sorting on dune evolution, providing novel insights into the morphological maintenance mechanisms of complex dunes in hyper-arid environments.