NOVELTY - Method for preparing environmentally responsive mesoporous silicon nanoparticles, involves (a) dissolving template agent in sodium hydroxide solution, adding ethyl orthosilicate, performing vacuum drying to obtain mesoporous silicon nanoparticles, (b) dispersing mesoporous silicon in methylbenzene to obtain the amino-modified mesoporous silicon nanoparticles, (c) adding polyelectrolyte, and (d) placing biological active molecules in buffer solution, adding surface self-assembly modified mesoporous silicon nanoparticles, and drying the particles.    USE - The method is useful for preparing environmentally responsive mesoporous silicon nanoparticles.    ADVANTAGE - The simple method prepares preparing environmentally responsive mesoporous silicon nanoparticles with excellent biological compatibility and is cost-effective.    DETAILED DESCRIPTION - Method for preparing environmentally responsive mesoporous silicon nanoparticles, involves (a) dissolving template agent in sodium hydroxide solution at 50-95 degrees C, adding ethyl orthosilicate, stirring and mixing the mixture, filtrating the mixture, drying the mixture, refluxing the ethanol to template, and performing vacuum drying to obtain mesoporous silicon nanoparticles, where the mole ratio of the template agent, sodium hydroxide and ethyl orthosilicate is 1-2:3-58:7-9, (b) dispersing mesoporous silicon in methylbenzene, adding 3-aminopropyl triethoxysilane to react in the nitrogen protection, and drying the product to obtain the amino-modified mesoporous silicon nanoparticles, where the mole ratio of mesoporous silicon, 3-aminopropyl triethoxysilane and methylbenzene is 4:6:0.5-2:400-600, (c) preparing mesoporous silicon nanoparticles obtained in step (a) and amino modified mesoporous silicon nanoparticles obtained in step (b) as suspension, adding anionic polyelectrolyte or cationic polyelectrolyte solution and stirring the solution for 0.2-2 hours, centrifuging the mixture, dispersing the solution, repeating the process and further drying the solution to obtain surface self-assembly modified mesoporous silicon nanoparticles and (d) placing biological active molecules in the buffer solution having a pH of 2-8, adding surface self-assembly modified mesoporous silicon nanoparticles, stirring the solution for 4-20 hours, adjusting pH to 6-8 and stirring the solution for 0.2-2 hours, centrifuging the solution and drying the particles.