The disclosure provides a quantum dot light emitting device, a backlight module, and a display device. The quantum dot light emitting device arranged on a first substrate which is a printed circuit board of a display device includes at least one backlight light source and a quantum dot optical element, wherein the at least one backlight light source is arranged on the first substrate, and configured to emit light; and the quantum dot optical element is fixed by a bracket on the first substrate above the at least one backlight light source, and configured to transmit the light emitted by the at least one backlight light source; wherein the quantum dot optical element includes two second substrates arranged opposite to each other, at least two blocking layers arranged opposite to each other, and a plurality of quantum dots, wherein the at least two blocking layers are arranged respectively at edges of the two second substrates so that an airtight space is defined by the two second substrates and the at least two blocking layers; and the quantum dots are filled in the airtight space. There will be a smaller number of quantum dots in this disclosure, and thus there will be a lower cost.