The invention provides a light splitting structure, which comprises a horizontal laser tube and a vertical laser tube which are fixedly arranged on a fixing device together; a first light source and a first light splitting module arranged at the first height in sequence are arranged in the horizontal laser tube; the first light source is arranged at the rear of the horizontal laser tube, and after passing the first light splitting module, a first ray emitted from the first light source is split into a left emergent ray and a right emergent ray respectively emitted to the left side and the right side of the horizontal laser tube, therefore two horizontal datum points and a horizontal datum line emitted forwards are formed; a second light source and a second light splitting module arranged at the second height in sequence are arranged in the vertical laser tube; the second light source is arranged at the rear of the vertical laser tube, and after passing the second light splitting module, a second ray emitted from the second light source is split into an upper emergent ray and a lower emergent ray respectively emitted to the upper side and the lower side of the vertical laser tube, therefore two vertical datum points and a vertical datum line emitted forwards are formed.