The invention relates to a method for preparing anhydrous ethylenediamine from bisaminosilane by-product ethylenediamine hydrochloride, belonging to the technical field of fine chemicals. In the present invention, ethylenediamine hydrochloride and calcium oxide powder, the by-products of bisaminosilane, are stirred and neutralized at 80-115°C in the presence of ethylenediamine solvent, and directly distilled after the reaction to obtain a moisture content of 2%~ 3% water-containing ethylenediamine, then add water-containing ethylenediamine to calcium oxide powder under the action of a catalyst, stir and dehydrate at 100~115°C, and then distill to obtain anhydrous ethylenediamine with a moisture content of less than 0.2%. The invention has the advantages of simple equipment process, cheap and easy-to-obtain raw materials, safety and environmental protection, high product quality and low moisture content, can be directly used as raw materials, improves economic benefits, and is suitable for industrial production.