Due to the spectrum width of stimulated Brillouin gain, the best available spectral resolution is limited for the developed precision spectral analyzer based on the optical fiber stimulated Brillouin effect. In addition, the stimulated Brillouin gain coefficient is related to the power. These factors affect the performance of the NIR fiber Brillouin spectrometer. To solve these problems, the research is conducted and a spectral resolution enhancement method is proposed. In this method, two stages of stimulated Brillouin process are cascaded, combined with the power regulation of the measured light and the pump light, so that the stimulated Brillouin process is in the small signal linear high gain region. The results show that this method can achieve about 1.4 times spectral resolution enhancement. The spectral resolution enhancement method proposed in this paper breaks through the theoretical limitations and improves the performance of NIR fiber Brillouin spectrometer.