The disclosure provides a light emitting device and a manufacturing method thereof. The light emitting device includes a substrate, an LED chip, a quantum dot composite layer and a first protective layer; the LED chip is disposed on a surface of the substrate; the quantum dot composite layer is arranged on a surface of the LED chip away from the substrate; the first protective layer is arranged on a surface of the quantum dot composite layer away from the LED chip; wherein the quantum dot composite layer includes a water-soluble polymer matrix and quantum dots dispersed in the water-soluble polymer matrix; the material of the first protective layer is one of a first inorganic oxide and a first water-blocking polymer; and the material of the water-soluble polymer matrix is an oxygen-blocking polymer.