The mechanisms of the improved efficacy of drug delivery systems using nano carriers have been extensively researched. Previous studies have shown that nano and micro particles are easily taken up by a group of localized endothelial cells in the small intestine, especially by Peyeras patch. Therefore, the drug absorption is highly increased. In addition, the incorporation of the drug into particle core could protect it against the harsh environment in the gastrointestinal tract and thus increases the stability of the peptide drug. The controlled release of drug from carriers prolongs the blood circulation. Though there are many oral delivery systems developed for preclinical studies, none has been approved for clinical use yet. Even so, oral delivery of anti-osteoporotic protein/peptide drugs still remains a promising possibility.