A QLED device and manufacturing method thereof, a QLED display panel and a QLED display device are disclosed which improve the surface and internal structure of the quantum dot layer in the QLED devices. The method for manufacturing a QLED device includes forming a first electrode layer; forming a quantum dot layer on the first electrode layer; infiltrating a mixed solvent containing a bifunctional molecule into the quantum dot layer so as to improve the structure of the quantum dot layer; and forming a second electrode layer on the quantum dot layer.