In this paper,a high resolution optica l spectrum measurement technology based on stimulated Brillouin scattering (SBS) in optical fibers is presented.A continuo usly tunable distributed feedback (DFB) laser is used as pump source.It i nteracts with signal li ght under test in single mode optical fibers via stimulated Brillouin amplification effect.The wavelength scanning of DFB laser is achieved by high precision temperature tuning.Compared with external-cavity tuning lasers used in previous similar studies,the DFB laser has many advantages,such as compact size,low cost,and b etter vibration resistance performance.In order to improve the measurement precision,the outpu t light of DFB laser in tuning is self-beat and the beat frequency is process ed to determine the real-time sweep velocity and wavelength.The feasibility of the high precision optical spectrum measuremen t technology is demonstrated in the measurements of two lasers,and the optical s pectrum resolution of about 0.24pm is obtained.