Based on the traditional distributed optical fiber sensing technology that uses back Rayleigh scattering, a linear sweep pulse modulation method for micro-seismic detection is proposed. The rectangular pulse in the modulation system is first transformed into a linear sweep pulse, and long-distance and high-spatial-resolution sensing is realized by compressing the pulse and matching filtering. Through simulation and experimental verifications, a narrow line-width laser with a line width of approximately 10 kHz is selected as the light source. Electro-optical and acousto-optical modulations determine the frequency scanning range and time as 5.6‒5.8 GHz and 2 μs, respectively. Linear sweep signal modulation obtains a sensing distance of 10 km, and the intensity range of the received back Rayleigh scattering signal is -60~-50 dBm.