A light-emitting device (1) and a related light source system. The light-emitting device (1) comprises a laser light source (11, 21, 31) and a light collecting system (12, 22). The laser light source (11, 21, 31) comprises a first laser array (111, 211, 311) and a second laser array (112, 212, 312) for respectively generating a first light and a second light with different wavelength ranges. The light collecting system (12, 22) is used for collecting the light emitted from the laser light source arrays. The ratio of the divergence angle of the collected second light to that of the first light is less than or equal to a predetermined value. The predetermined value is 0.7. The light-emitting device (1) is capable of generating two kinds of light beams with different etendues.