Poly(vinylidenefluoride-tetrafluoroethylene), P(VDF-TFE)and poly(vinylidenefluoride-hexafluoroacetone), P(VDF-HFA) were blended, both of which were crystalline polymers. The crystal structures of the blends were investigated using X-ray diffraction. The samples containing the rich P(VDF-TEE) showed the crystal structure of only the polar phase, whereas those containing the rich P(VDF-HFA) showed the mixed crystal structure of $alpha$ and $eta$ phases. The piezoelectric properties of the blends were measured to investigate the origin of piezoelectricity and the mechanism of dipole reorientation. The piezoelectricity may be originated from the residual polarization and the internal strain of the samples. The 180$^{circ}$rotation of dipoles was supported by the fact that the measured value of the maximum polarization agrees with the calculated value using the frozen dipole model.