The invention discloses a method for sensitively and quickly detecting MiRNA by a metal-enhanced fluorescent/colorimetric dual-mode biosensor based on a dual-functional nano material. Through the use of the dual-mode biosensor, the accuracy of the detection results are improved; moreover, the dual-functional nano material has excellent magnetic performance and enhanced fluorescent performance, so that not only can the recycling problem be solved, but also the detection sensitivity is greatly improved. Finally, through specific binding and magnetic separation of the MiRNA and template DNA, sediment is used for recirculation, and a supernatant is used for colorimetric detection, so that the visual, highly sensitive, simple, quick and energy-saving MiRNA detection can be realized.