A light emitting device and system includes an LED for emitting the first light, an excitation light source for emitting excitation light, and a wavelength conversion layer applied on the light emitting face of the LED. The wavelength conversion layer can not be excited by the first light, and can be excited by the excitation light to emit the second light. The light emitting device further includes a light path separating device arranged in the light path between the wavelength conversion layer and the excitation light source. The light path separating device is used for guiding the excitation light to the wavelength conversion layer, and in order to form the output light of the light emitting device, guiding the mixed light emitted by the wavelength conversion layer to be separated from the path of the excitation light, wherein the mixed light comprises the first and second light. Such light emitting device and system utilizes the light reflection effect of the LED itself, thereby realizing the mixture of the first light emitted by the LED and the second light generated by the wavelength conversion layer applied on the surface of the LED without enlarging the light emitting area of the light source.