Objective To evaluate the biomechanical properties of the callus during osteoporotic fracture healing with the treatment of low-intensity pulsed ultrasound (LIPUS) in rats. Methods Forty-two female SD rats of 4.5-month-old were involved in the study ,36 of which underwent bilateral ovariectomy. Ten weeks later when the osteoporosis was confirmed, the 36 rats had their bilateral femoral shaft closely fractured. After serious selection only 26 rats finally entered the experiment. On the day after fracture, a hind limb was chosen randomly to receive LIPUS as treatment withthe other limb as control. The LIPUS was done 20 minutes daily with a 200μsec burst of 1.5MHz sine waves repeated at 1kHz and an average intensity of 50mW/cm2. The rats were sacrificed on 4, 6, 8, 12 weeks after treatment, respectively, and their bilateral femurs were taken for biomechanical analysis with three point bending test. Results When compared with the control side on 4, 6, 8, 12 weeks after LIPUS treatment, respectively, the peak load of the callus in treated side was higher about 58.75%, 76.53%, 37.04%, 22.14%, the peak stress was higher about 29.21%, 66.43%, 29.08%, 16.90%, and the elastic modulus was higher about 34.01%, 61.04%, 46.15%, 31.77%. Except for the peak stress in 4 weeks and the elastic modulus in both 4 and 6 weeks, all the differences were significant (P<0.05), especially for the peak load in 6 weeks and the peak stress in 8 weeks (P<0.01). Conclusions LIPUS can improve the biomechanical properties of the callus during the osteoporotic fracture healing in rats, thus providing a new way to treat osteoporotic fractures clinically.