The invention relates to a piezoelectric energy harvester applied to pipeline fluid monitoring, and belongs to the fields of new energy and piezoelectric power generation. Impellers are positioned onthe inner wall, which passes through one end of a shaft, of a pipeline, and are positioned in the center of the pipeline; strip-shaped permanent magnets are arranged at the other end of the shaft, andare positioned on the outer wall of the pipeline; the shaft is supported by a bearing and a bearing pedestal and vertically mounted above the pipeline; each piezoelectric vibrator consists of a metalsubstrate, a piezoelectric sheet and the strip-shaped permanent magnets in a gluing manner; one end of the metal substrate is connected with the interior of the metal shell, the free end is connectedwith the permanent magnets, and the surface is glued with the piezoelectric sheet; and a circuit board is just mounted in the center of the interior of the shell, and the shell is mounted on the upper part of the pipeline. The piezoelectric energy harvester has the characteristics and advantages as follows: the stable piezoelectric energy harvester is formed by interaction force between the permanent magnets; and the piezoelectric energy harvester is simple in structure and process, low in cost, free of accelerated speed sudden change, high in vibration stability, high in power generation capability and high in reliability, and capable of improving electric energy production by increasing the number and prolonging the piezoelectric vibrators.