[en] Highlights: • Molybdenum oxide (MoOx) as hole injection layer was formed by solution process. • Flexible quantum dot light-emitting diodes with MoOx exhibit superior performance. • Stability/lifetime of the light-emitting devices is substantially improved. -- Abstract: In this paper, the aqueous solution-processed molybdenum oxide (sMoO_x) as an efficient hole injection layer for flexible quantum dot light emitting diodes (QLEDs) was prepared using a simple, low-cost and non-toxic solution method. Compared to the traditional device used poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as hole injection layer, the flexible QLED with modified sMoO_x film has a higher maximum current efficiency, 5.46 cd/A. In addition, the stability and lifetime of flexible devices are improved effectively with the use of inorganic molybdenum oxide as hole injection layer, and they presented excellent flexibility through the repeated mechanical bending test at 5 mm radius of curvature.