The scheme of measuring Brillouin frequency shift in fiber sensor based on edge optical filter is proposed. The factors affecting on the measurement accuracy of Brillouin frequency shift are analyzed, the relation between the measurement of Brillouin frequency shift and signal to noise (SNR) is obtained. The results indicate that, under the thermal noise approximation, the measurement accuracy of Brillouin frequency shift is dependent on thermal noise, the derivative of the transmission function of the edge...