A light emitting device includes a light source module comprising an excitation light source for emitting exciting light and a compensation light source for emitting compensation light; and a color wheel component, comprising at least one segmented region distributed in a motion direction of the color wheel component. The color wheel component emits the compensation light and first light that comprises at least one beam of excited light under irradiation of the excitation light source and the compensation light source. The compensation light spectrally overlaps the at least one beam of excited light in the first light, and the compensation light and the excited light spectrally overlapping the compensation light are simultaneously emitted and are independently adjustable. A projection system comprising a light emitting device is further provided.