The invention provides a porous magnetic 
chitosan gel 
microsphere with controllable particle size based on an in-situ co-
precipitation principle and a preparation method thereof. The preparation method comprises the following main steps: firstly, carrying out a complexation reaction on a 
mixed solution of Fe<2+>, Fe<3+> and 
chitosan to prepare precursor-induced pre-
sol; secondly, dropwise dripping the pre-
sol into an alkaline soaking solution containing NaOH, 
sodium citrate and the like for coprecipitating to generate nano-Fe3O4; thirdly, carrying out a crosslinking reaction on the pre-
sol and then curing, wherein the 
crosslinked chitosan gel 
microsphere is of a porous reticular structure and the Fe3O4 is uniformly distributed in the 
chitosan gel 
microsphere. The particle size of the chitosan gel microsphere is controlled by adjusting the rotating speed of a 
peristaltic pump and the concentration of the solution. The chitosan gel microsphere prepared by the method has the advantages of abundant pores, large specific surface area, and high adsorption and 
acid resistance; in addition, the preparation method has the characteristics of simplicity, wide source in raw materials, low cost, easiness in separation and 
recovery, no secondary 
pollution and the like. The porous magnetic chitosan gel microsphere disclosed by the invention can be used for enrichment, 
recovery and 
contamination remediation of metals in mines, 
smelting plants, electronic factories, 
electroplating plants and radioactive 
wastewater.