The current situation of narrow line-width lasers is briefly introduced. In view of the domestic market dependence on imports of lasers a homebred distributed feedback fiber laser with narrow line-width is realized by developing active phase-shifting fiber grating fabrication technology, solving the sound insulation and vibration isolation package technology, and designing a power amplification optical path of single pump. The prototype power is 35mW, linewidth is less than 3 kHz, relative intensity noise is less than -115 dB/Hz. The main technical indicators are close to advanced foreign products such as NKT and NP. The prototype is applied to the distributed optical fiber sensing system, it can realize good sensing signal demodulation, and the use system is much lower than imported products.