In order to reduce the harm of waste water treatment membrane to the environment, this work used biodegradable polymer as the base material to develop the application of environmentally friendly materials in water treatment. For improving the separation efficiency and mechanical performance of the membrane, the chitosan (CS) coating layer and the electrospun polylactic acid (PLA) fiber substrate layer were compounded by dip-coating which formed the CS/PLA filter membrane. On the study of the ratio of CS and PLA, it was found that when the volume ratio of CS to PLA was 7 to 5, the surface of CS coating was dense and flat, and the thickness of CS dense layer was 7 μm. At this time, the pure water flux and mechanical tensile properties of CS/PLA composite membrane were the optimum. The permeability of this composite membrane to acid dye was 99.34 L/(m2?h) and the adsorption rate reached to 96%. The adsorption rates of bovine serum albumin and ovalbumin were 86% and 84%, respectively. The adsorption capacities of composite membrane for Cu2+, Pb2+ and were 165.00, 248.54 and 307.83 mg/g, respectively. The above experimental results provide technical methods and ideas for the application of CS/PLA biomembrane in industrial dye recovery, protein separation with different molecular weight and metal ion removal.