To study the effects of different frequency sinusoidal electromagnetic fields on the bone mineral density and bone histomorphometry of SD young rats, and to screen suitable electromagnetic field frequency. In total 32 female SD rats of 8 weeks old were randomly divided into 4 groups: control group, 15 Hz group, 30 Hz group and 45 Hz group. Except for the control group, rats in experimental groups were treated with corresponding frequency of 1.8 mT sinusoidal electromagnetic field 90 minutes every day. Rats were measured for bone mineral density after 8 weeks by dual energy X-ray absorptiometry. Rats’ femur and vertebral bones were measured by analyzing the static and dynamic forms on the right tibia bone for morphometrics. Rat serum was measured to estimate the index of bone formation and bone resorption. Bone mineral density of rats from 15 Hz group and 45 Hz group was higher than that of the control group (P<0.05). Serum osteocalcin level of rats from 15 Hz group and 45 Hz group was higher than that of the control group (P<0.05). Double fluorescence spacing and static parameters of bone tissue in experimental group rat tibia were higher than that of the control group (P<0.05). Our findings imply that 15 Hz and 45 Hz sinusoidal electromagnetic fields can effectively increase bone mineral density in young rats for preventing osteoporosis.