The invention relates to preparation and applications of mesoporous silica / insulin nanoparticles modified by phenylboronic acid, for effectively solving the problem that the traditional drug carriers release medicines unidirectionally. The technical scheme is as follows: the preparation comprises the following steps: firstly, synthesizing mesoporous silica nanoparticles, modifying amino groups on the surfaces of the mesoporous silica nanoparticles, loading medicine insulin in the mesoporous structure through physical absorption, and further modifying with phenylboronic acid and polysaccharide, thus obtaining the mesoporous silica / insulin nanoparticles modified by phenylboronic acid. The preparation and applications have the advantages that the synthesis process is simple, the prepared nanoparticles have the good biocompatibility, and the releasing valve of medicines can be repeatedly opened and closed, so that the sustained-release effect is achieved on the release of medicines; the mesoporous silica / insulin nanoparticles have a long-time circulation in the body, so that the administration times can be reduced, and thus the mesoporous silica / insulin nanoparticles belong to an innovation in diabetes treatment medicines.