The invention discloses a preparation method of a modified 
polymer film material for effectively removing trace heavy 
metal ions in a 
water body, which comprises the following steps: 1) carrying out 
plasma treatment on a 
polymer film; 2) respectively preparing an initiator solution, a 
monomer solution, a 
buffer solution, an activating solution and a 
polyethylene polyamine water solution; 3) immerging the 
polymer film in the initiator solution, and carrying out surface activation by 
ultraviolet irradiation; 4) putting the polymer film into the 
monomer solution to carry out 
grafting reaction under 
ultraviolet irradiation; 5) activating the polymer film in the activating solution; and 6) putting the activated film into a 
polyethylene polyamine water solution to carry out 
coupling reaction, thereby preparing the modified 
film material capable of removing trace heavy 
metal ions in a 
water body. In the polymer film modifying process, carboxyl and amino groups are introduced to carry out 
hydrophilization and endow the modified film with complexing capacity, thereby removing the trace heavy 
metal ions. The invention has the advantages of simple technique, favorable 
treatment effect, wide application range, low cost, high 
unit mass adsorption capacity, time saving, high efficiency and energy saving.