The invention provides a preparation method of a polarization-free piezoelectric base electro-mechanical conversion element. The preparation method of a polarization-free piezoelectric base electro-mechanical conversion element includes the steps: after grinding the piezoelectric fiber prepared through electrostatic spinning into a fiber rod with a suitable length, mixing the fiber rod with polydimethylsiloxane (PDMS), taking the mixed material as the main material of the electro-mechanical conversion element; maintaining the length of the fiber rod in the range of 2-3 micrometers, by means of control of the grinding time; and according to a piezoelectric force microscope, analyzing the piezoelectric and ferroelectric performance of fiber, so that the fiber short rod with the length can maintain single spontaneous polarized orientation. For the preparation method of a polarization-free piezoelectric base electro-mechanical conversion element, through an optimized spin coating technology, by means of control of the rotation speed of spin coating, under the synergistic effect of gravity and centrifugal force, the piezoelectric fiber rod can be dispersed uniformly in the liquid-state polydimethylsiloxane, and the length direction of the fiber rod is parallel to the substrate; and under the effect of the electrostatic force, self-assembling is performed among the fiber rods in the spontaneous polarized direction. Therefore, the prepared electro-mechanical conversion element with the Sandwich structure can generate 10V high voltage output under the bending strain, without the polarization process. The preparation method of a polarization-free piezoelectric base electro-mechanical conversion element is simple and effective, and can realize volume production.