The invention relates to a self-excited pipeline fluid piezoelectric energy harvester, and belongs to the field of piezoelectric power generation. An inner wall of a pipeline is provided with a spoiler and a shell through spoke plates; end covers with bosses are arranged at two ends of a cylinder wall of the shell; a connection block is arranged at one end of a pin shaft and the other end extends outside from the shell through the left end cover and is provided with an exciter; a pin shaft is sleeved with a balance spring and a limiting spring; the balance spring abuts on the exciter and the left end cover; the limiting spring abuts on the left end cover and the connection block; a circuit board is arranged on the connection block; each piezoelectric vibrator is formed by splicing a metal substrate and piezoelectric plates; two ends and the middle part of the substrate are fixed on the left boss and the right boss and the connection block respectively; each straight piezoelectric vibrator becomes a bent structure after being assembled; and the piezoelectric crystal plates endure pressure stress. The self-excited pipeline fluid piezoelectric energy harvester has the features and advantages that the straight piezoelectric vibrators are arranged into the bent structure and form the self-excited stretching vibration energy harvester, so that the structure and the technology are simple and the cost is low; the piezoelectric crystal plates only endure the pressure stress with a controllable range and the reliability is high; and the generating capacity is easily improved by increasing the number and the lengths of the piezoelectric vibrators.