The invention discloses a preparation method of strong base type ion exchanging fibers. The method comprises the following steps: adding base fibers to a reaction vessel; then adding a solvent A, andfully swelling; adding cyanuric chloride and a catalyst after swelling; uniformly stirring and heating to react; cooling until room temperature is reached after reaction; filtering to obtain a product; sequentially processing the obtained product by soaking, extracting, washing with water and drying to obtain cyanuric chloride modified fibers; adding the cyanuric chloride modified fibers to a solvent B to fully swell; then sequentially adding a functional agent and an acid-binding agent after swelling; uniformly stirring and heating; cooling until room temperature is reached after reaction; filtering to obtain a product; sequentially processing the obtained product by soaking, extracting, washing with water and drying to obtain the strong base type ion exchanging fibers. According to the method for preparing the strong base type ion exchanging fibers, the use defect that strong cancerogenic substances such as chloromethyl ether are used in chloromethylation process in the prior art canbe effectively avoided.