The present invention discloses a method for preparing 
drug-loaded 
chitosan nano-microspheres, wherein 
sorbitan sesquioleate is adopted as an emulsifying agent, 
vanillin is adopted as a cross-linking agent, and an emulsifying and cross-linking method is adopted. The method comprises: dissolving a certain amount of 
chitosan and a certain amount of 5-
fluorouracil in a certain amount of an 
acetic acid solution with a 
mass fraction of 1%; after completely dissolving, slowly adding the resulting solution to a certain amount of a 
liquid paraffin oil phase, and rapidly stirring at a 
room temperature to form a white emulsus water-in-
oil emulsion, wherein the resulting solution is adopted as the water phase, the 
liquid paraffin oil phase contains a certain amount of an emulsifying agent; adding a certain amount of a cross-linking agent solution to the 
reaction system, and continuously stirring for a certain time; carrying out 
centrifugal separation, collecting the prepared 
drug-loaded nano-microspheres, completely washing respectively by 
petroleum ether and 
acetone, carrying out 
freeze drying to obtain the yellowish 
drug-loaded 
chitosan nano-
microsphere powder, wherein the particle size of the prepared drug-loaded chitosan nano-microspheres is 100-150 nm, the 
sphericity is good, the 
controlled release effect is good, the encapsulation efficiency is 90-96%, the drug 
loading rate is 20-25%, and the drug-loaded chitosan nano-microspheres can meet clinical oral requirements and injection requirements. In addition, the method has a simple process, and is applicable for the large-scale production.