The invention provides a technology for preparing folic acid-glucan-camptothecin composite nanoparticles through a supercritical CO2 anti-solvent method. The technology comprises the following main steps of: A. firstly coupling folic acid and glucan; B. feeding supercritical CO2 into a crystallization kettle, and reaching a preset temperature and preset pressure intensity; C. dissolving the glucan coupled with the folic acid and camptothecin in dimethyl sulfoxide according to certain proportions, spraying the solution into the crystallization kettle by a spray nozzle through a high-pressure liquid pump, and settling out the particles; and D. after stopping the spraying of the solution, continuously feeding the supercritical CO2 so as to clean the residual dimethyl sulfoxide, finally reducing temperature and emptying, and collecting powder, wherein the obtained powder is the folic acid-glucan-camptothecin composite nanoparticles. The folic acid-glucan-camptothecin composite powder obtained by the method has good water solubility, high tumor targeting, low toxicity and slow-release characteristic, and the particle size range of the powder is 100-750nm.