A light source system, comprising an excitation light unit (301, 303), a spectral filter unit, a scattering unit (305, 306), and an excited-light unit (307, 308), wherein the excitation light unit (301, 303) is configured to emit excitation light to the spectral filter unit; the spectral filter unit is configured to reflect/transmit a portion of the excitation light from the excitation light unit (301, 303) to the scattering unit (305, 306); the scattering unit (305, 306) is configured to scatter the portion of the excitation light to produce a first light having a first polarization state and a second light having a second polarization state, and emit the first light and second light to the spectral filter unit; the spectral filter unit is configured to transmit/reflect the second light from the scattering unit (305, 306); the spectral filter unit is further configured to transmit/reflect another portion of the excitation light from the excitation light unit (301, 303) to the excited-light unit (307, 308), and the excited-light unit (307, 308) produces excited light under the illumination of the portion of the excitation light and emits the excited light to the spectral filter unit; and the spectral filter unit is further configured to reflect/transmit the excited light from the excited-light unit (307, 308), so that the spectral filter unit merges and emits the transmitted second light and the reflected excited light therefrom, or merges and emits the reflected second light and the transmitted excited light therefrom; wherein the spectral filter unit comprises at least one beamsplitter; characterized in that a surface of the beamsplitter facing the excitation light unit and the scattering unit is a first surface, and a surface of the beamsplitter facing the excited-light unit is a second surface; a second surface of at least one of the beamsplitters is coated with a film for transmitting the second light and reflecting the excited light, or a second surface of at least one of the beamsplitters is coated with a film for reflecting the second light and transmitting the excited light; wherein some surfaces of the at least one beamsplitter except the second surface are coated with a film for reflecting the first light and transmitting the second light, or are coated with a film for transmitting the first light and reflecting the second light. the excitation light unit (301, 303) is configured to emit excitation light to the spectral filter unit; the spectral filter unit is configured to reflect/transmit a portion of the excitation light from the excitation light unit (301, 303) to the scattering unit (305, 306); the scattering unit (305, 306) is configured to scatter the portion of the excitation light to produce a first light having a first polarization state and a second light having a second polarization state, and emit the first light and second light to the spectral filter unit; the spectral filter unit is configured to transmit/reflect the second light from the scattering unit (305, 306); the spectral filter unit is further configured to transmit/reflect another portion of the excitation light from the excitation light unit (301, 303) to the excited-light unit (307, 308), and the excited-light unit (307, 308) produces excited light under the illumination of the portion of the excitation light and emits the excited light to the spectral filter unit; and the spectral filter unit is further configured to reflect/transmit the excited light from the excited-light unit (307, 308), so that the spectral filter unit merges and emits the transmitted second light and the reflected excited light therefrom, or merges and emits the reflected second light and the transmitted excited light therefrom; wherein the spectral filter unit comprises at least one beamsplitter; a surface of the beamsplitter facing the excitation light unit and the scattering unit is a first surface, and a surface of the beamsplitter facing the excited-light unit is a second surface; a second surface of at least one of the beamsplitters is coated with a film for transmitting the second light and reflecting the excited light, or a second surface of at least one of the beamsplitters is coated with a film for reflecting the second light and transmitting the excited light; wherein some surfaces of the at least one beamsplitter except the second surface are coated with a film for reflecting the first light and transmitting the second light, or are coated with a film for transmitting the first light and reflecting the second light.