Silicon-based detector has the advantages of stability and reliability, low dark current, high response and low price. It is widely used in photoelectric detection and other fields. In view of the limited detection ability of silicon-based detector in the ultraviolet band, a concentrating structure which can enhance the detection ability of silicon-based detector in the ultraviolet band is designed in this paper. First, the absorbed ultraviolet light is transformed into visible light by using the fluorescence characteristics of ZnCdS∶Mn/ZnS quantum dots. Then, combined with the short wave pass cut-off color filter film, the external quantum efficiency of the detector in the 260-400 nm band is greater than 20%, the response time is limited to the order of ms, and the dark current is limited to the order of pA. The experimental results show that the focusing structure of quantum dots layer can significantly improve the detection ability of silicon-based detector in the ultraviolet band. In addition, the silicon-based detector with adjustable detection range can be realized in the ultraviolet band by changing the size of quantum dots.