The invention relates to a 
chitosan macromolecule composite membrane and a preparation method, in particular to a preparation method of a dithiocarbamic acid (DTC) modified 
chitosan macromolecule composite membrane. The 
composite membrane is used for efficiently removing heavy 
metal ions in 
industrial waste water. The preparation method concretely comprises the following steps of (1) 
chitosan acetic acid solution is prepared: chitosan with the deacetylation degree greater than 90 percent is dissolved into 
acetic acid water solution with the 
mass concentration being 1 to 5 weight percent, 
solid impurities in the solution are removed after still standing, and chitosan 
acetic acid solution with the 
mass concentration being 1 to 10 weight percent is obtained; (2) crosslinking agent solution is prepared: 
glutaraldehyde is adopted as the crosslinking agents, and the 
mass concentration range of 
glutaraldehyde water solution is 0.2 to 2 weight percent; (3) the chitosan 
acetic acid solution and the crosslinking agent solution are mixed according to a 
mass ratio being (5-1):1 and are coated on a 
macromolecule support membrane, and the 
coating thickness is in a range being 0.1 to 0.25 mum so that the cross-linking reaction is generated; (4) prepared semi-finished product membranes take reaction with 
carbon disulfide, the 
mass ratio of the added 
carbon disulfide to chitosan is (10-4):1, DTC is grafted on the surface, then, the 
drying is carried out, and the DTC modified chitosan macromolecule composite membrane is prepared. The DTC modified chitosan macromolecule composite membrane and the preparation method have the beneficial effects that the DTC modified chitosan macromolecule composite membrane combines the advantages of 
mechanical strength and stability of the macromolecule support membrane, meanwhile, the excellent chelating heavy 
metal ion performance of the DTC chitosan is realized, the 
treatment effect on heavy 
metal ion waste water is good, the membrane is directly soaked in waste water containing the heavy metal ions to realize the absorption treatment, the operation is simple, the effect is excellent, in addition, the regeneration is easy, the repeated use can be realized, and the cost is greatly reduced.