Traditional Chinese medicine (TCM) can help prevent or treat diseases; however, there are few studies on the active substances of TCM. For example, Lycium barbarum L. has been proven to be effective in treating osteoporosis for thousands of years, but its active substance remains to be unknown. Prompted by the efforts to modernize TCM, the present study focused on the novel active substance of Lycium barbarum L. to reinforce kidney essence to produce bone marrow. Illumina deep sequencing analysis and stem-loop polymerase chain reaction (PCR) assay revealed that miR162a, a Lycium barbarum L.-derived microRNA, can pass through the gastrointestinal tract to target the bone marrow in mice. Immunofluorescence staining showed that miR162a was absorbed through systemic RNA interference defective transmembrane family member 1 (SIDT1) in the stomach. Bioinformatics prediction and luciferase reporter assay identified that miR162a targeted nuclear receptor corepressor (NcoR). Alizarin red staining and micro-computed tomography (microCT) confirmed that miR162a promoted osteogenic differentiation in bone marrow mesenchymal stem cells, zebrafish, and a mouse model of osteoporosis. In addition, transgenic Nicotiana benthamiana (N. benthamiana) leaves overexpressing miR162a were developed by agrobacterium infiltration method. microCT and tartrate-resistant acid phosphatase staining confirmed that transgenic N. benthamiana leaves effectively protected against osteoporosis in mice. Our study mechanistically explains how Lycium barbarum L. improves osteoporosis and supports that Lycium barbarum L. reinforces kidney essence, thereby strengthening the bone. miR162a expressed by transgenic plants may represent a novel and safe treatment for human osteoporosis.