The bending characteristics of distributed feed back fiber lasers were investigated. Firstly, a theoretical model of fiber lasers output wavelength and bending radius was presented. It shows a linear correlation between the output wavelength variation of fiber lasers and the inverse square of the bending radius, and as the bending radius increases, the Bragg wavelength experiences a blue shift. In corresponding experiments, 3 fiber lasers were used to test output wavelength with bending radii between 10 mm and 90 mm; these experiments demonstrate the accuracy of the theoretical analysis. Secondly, fiber lasers output power and bending radius were studied. One fiber laser was used as reference to eliminate environmental interference. The experiment shows fluctuation ranges of fiber lasers output power are less than 2 dB during the experimental time in 32 days. Finally, the slope efficiency is investigated, showing excellent bending insensitivity. The results provide an important reference for DFB fiber lasers in applications of bending sensing.