For the problems that a large quantity of organic solvents and pore-foaming agents which are difficult to recycle are used in the traditional membrane preparing process, environmental 
contamination is caused, the pore size distribution of membranes is wide, and the membranes lack of responsiveness, the invention provides a narrow pore size distributed hydrophilic filtering membrane sensitive to temperature and pH on the basis of the idea of 
bionics by taking a 
metal chloride saline solution as the 
solvent. A preparation method of the membrane comprises the steps that 
fibroin is grafted with 
polyacrylonitrile and poly(N-isopropylacrylamide) in a homogeneous mode, and a membrane 
casting solution is obtained; the membrane 
casting solution is put into a water coagulating bath, 
metal ions and 
chloride ions are gradually scattered in water, an the 
fibroin grafted with poly(N-isopropylacrylamide) and 
polyacrylonitrile is subjected to phase transformation to form the membrane. The 
metal ions and the 
chloride ions play the role of hole forming, the 
fibroin, poly(N-isopropylacrylamide) and 
polyacrylonitrile are subjected to microphase separation, and water channels subjected to 
ion hole forming are formed in the interface. By means of the fibroin and poly(N-isopropylacrylamide), the pH value sensitivity and 
temperature sensitivity of the membrane are achieved. By means of the hole forming effect of the metal ions and the chloride ions, the 
hole size of the membrane is smaller, and the 
hole size distribution is narrow.