The invention provides a folic acid and polydopamine modified tumor targeted mesoporous silica nanoparticle and a preparation method and application thereof. The preparation method particularly comprises the following steps: (1) dissolving mesoporous silica and a chemical in a solvent, performing a full reaction, and performing separation; (2) adding mesoporous silica initial nano-particles obtained in the step (1) in a solution, adding dopamine hydrochloride, performing a full reaction, and performing separation; and (3) adding the dopamine hydrochloride coated mesoporous silica initial nano-particles loaded with the chemical in a weakly basic water solution, sequentially adding a reducing agent and polyethylene glycol modified sulfydryl grafted targeted ligand folic acid, performing a full reaction, then performing separation to obtain the folic acid and polydopamine modified tumor targeted mesoporous silica nanoparticle. The preparation method of the folic acid and polydopamine modified tumor targeted mesoporous silica nanoparticle is simple, and favorable tumor targeting ability, biocompatibility and biodegradability are achieved.