Bone densitometry is usually performed by ultrasound or X-ray, which generally has no significant side effects. However, due to the trace radiation of X-ray, ultrasound should be used as much as possible when examining children. Ultrasonic bone densitometry utilizes the emission and attenuation of ultrasound waves to reflect calcium deposition, and can provide a good examination of bone density and bone structure changes. Since ultrasound does not emit radiation to the body, there are generally no significant side effects. Dual-energy X-ray bone densitometry, mainly the use of trace X-ray penetration of bone energy difference, to determine the bone condition, although its presence of radiation is very small, children to avoid as much as possible to reduce the harm when the examination. In conclusion, bone densitometry generally has no significant side effects, but ultrasound should be used as much as possible to avoid X-ray radiation when examining children.