Multicolor CCD photometric technology has been widely used in astronomical observations owing to its practicability， simplicity， and effectiveness； however， the issue of simultaneity needs to be addressed. In this paper， a new type of simultaneous three-channel photometric system， which uses a dichroic mirror to realize light splitting in the g′， r′， and i′ bands of the Sloan Digital Sky Survey （SDSS）， is introduced. First， the optical system of the three-channel photometer was simulated and analyzed by Zemax. The results showed that the system satisfied the overall design criteria and met the requirements for its intended application. Then， we observed a large number of SDSS standard stars to evaluate the optical performance of the equipment. The results indicated that the equipment could achieve simultaneous imaging within a field of view of 21.5′×21.5′， 21.5′×21.5′， and 21.3′×21.3′ in the g′， r′， and i′ channels， respectively. The system efficiency for each channel was 65.6， 68.3， and 63.7%， respectively， and the limiting magnitude of each channel was 15.26， 16.39， and 15.63， respectively， when the exposure time and signal-to-noise ratio were 1 s and 5， respectively. In the future， we will improve the detection capability of limiting magnitudes by optimizing the system.