In order to monitor the bending deformation of buried pipelines due to geological instability, a method of polyethylene(PE) pipeline microbending detection based on Brillouin optical frequency domain analysis(BOFDA) technology is proposed in this paper. The fiberglass substrate strain cable is laid along the wall of the pipe to make the fiber and the pipe deform together. The Brillouin frequency shift is used to calculate the stress variation of the fiber, and conjugate beam reconstruction algorithm is used to invert the bending disturbance of the pipe. The experiment resulshows that this method can distinguish and measure the direction and displacement of pipe bending very well, and the error is less than 0.4 cm, which improves the digital safety monitoring and early warning level of pipe.