Cubic beamsplitter, coated with a layer of film on the slope of the rectangular prism, and then glued together with a similar rectangular prism to form a cubic beamsplitter. The astigmatism of the flat beam splitter can be avoided, the coating is not directly exposed, and it is not easy to be damaged and corroded. Compared with flat beamsplitters, beamsplitters have equal optical paths for reflected and transmitted light. When transmitting light, the beam splitting prism has no effect caused by light deviation, so there will be no problems of beam translation, ghost image and interference. For spectroscopic and imaging. No need for long calibration at 45° angle of incidence.