Poly-Si film, due to its favorable piezoresistive properties, has been widely used in piezoresistive sensors. The previous researches have shown that the ultra-thin poly-Si film have better piezoresistive properties than common poly-silicon film, and have promising future of application. A promising method to obtain large grained high quality poly-silicon films by low-temperature crystallization of an amorphous precursor material is the aluminum-induced layer exchange (ALILE). In this paper, ultra-thin poly-Si films were prepared by aluminum induced layer exchange (ALILE). Experimental results of Raman spectroscopy show that a narrow and symmetrical Raman peak at the wave number of about 518 cm-1 was observed for all samples, indicating that the films were fully crystallized. XRD results show that the crystallites of ultra-thin poly-silicon layer were preferably (111) and (220) oriented. Hall affect measurements show that hole concentration of the films (p-type) were between 9×1018 and 6×1019 cm-3. Restorative properties show that the piezoresistors exhibit gauge factors (GFs) up to 60, with temperature coefficients of GF (TCGF) between -0.17～0%℃ and temperature coefficients of resistance (TCR) between -0.2 and -0.1%℃. The study of the ultra-thin poly-Si films by ALILE is completed, and the study results lay a foundation for application of the film to piezoresistive sensor.