In this paper, a silver modified micro-cavity fiber surface-enhanced Raman scattering (SERS) probe was proposed. Using Rhodamine 6G (R6G) solution as the probe molecule, the wet detection method was used to place the fiber SERS probe directly into R6G, and the far-end experimental performance of the prepared fiber SERS probe was studied. A micro-cavity fiber structure was fabricated by etching of hydrofluoric acid (HF). By controlling HF's etching time, a series of fiber structures with different etching times and different micro-cavity lengths were obtained. The effect of the length of the micro-cavity on the fiber SERS probe's performance was studied experimentally. The R6G with a 10^-3 mol·L^-1 concentration was used as the probe molecule. The mixing of the nano silver sol and the R6G was continuously optimized, and the structure of bare fiber micro-cavity was used for Raman detection of the mixed solution. It was found that the Raman signal was highest when the mixed order and the ratio of the mixed solution were the equal volumes of nano silver sol and R6G solution. The obtained mixed solution was used to find the -fiber micro-cavity structure parameters when the Raman signal enhancement effect was the highest. The experimental results showed that under the same experimental conditions, when the fiber's etching time was 5 minutes, the fiber micro-cavity structure had the best Raman signal enhancement effect. The average length of micro-cavities observed under the microscope for multiple sets of fiber was about 81 μm. For the obtained fiber micro-cavity structure, a series of silver nanofilm/multi-mode fiber (Ag/MMF) composite materials were fabricated by the magnetron sputtering technology with a controllable preparation process. When the magnetron sputtering time was 10 minutes, the fiber SERS probe (Ag/MMF-10) was obtained. In the experiment, deionized water was used to prepare different concentrations of R6G solutions. Using different concentrations of R6G as probe molecules, the remote detection limit (LOD) of the Ag/MMF-10 was as low as 10^-7 mol·L^-1. The detection of Raman signal reproducibility of Ag/MMF-10 showed that the relative standard deviation (RSD) of each characteristic peak was less than 10%. Simultaneously, the analytical enhancement factor (AEF) of Ag/MMF-10 to R6G with 10^-6 mol·L^-1 concentration can be as high as 2.64×10⁶. The experimental results showed that the Ag/MMF-10 had high sensitivity and good reproducibility. Therefore, the fiber SERS probe may have potential application value in trace detection, such as biomedical detection, chemical analysis of pesticide residues.