We grew 1.5-μm-thick Bi3.9Pr0.1Ti3O12 (BPT) polycrystalline films with a/b-axes orientation on IrO2/Si substrates from chemical solutions and measured electric-field-induced strain Є by a double-beam laser doppler vibrometer and atomic-force microscopy (AFM). The results reflected uniform film growth and elimination of elastic deformation of the substrate, and the microscopic piezoelectric response in AFM measurements agreed well with the macroscopic response evaluated by laser vibrometer. A large longitudinal Є=0.3% was observed at 400 kV/cm and 10 Hz, and the piezoelectric coefficient d33=dЄ/dE|0=60 pm/V was calculated. X-ray diffraction analyses revealed that the (200)/(020) peak of BPT was comprised of 40% a domain and led to the reduced values of ferroelectric polarizations of 2Pr=35 and Psat=23 μC/cm2. This suggests that applying an electric field did not cause fraction reconfiguration of a- and b-domains, and, therefore, the measured large strain was achieved without contribution from the 90°-domain-wall motion in a/b-axes-oriented BPT thick films.