The invention discloses a method for determining space by adopting an SAGD development well. The method utilizes a numerical simulation method, on the basis of fully considering geological parametersof a well spacing area and considering well drilling cost of the SAGD well and generation cost of accumulated steam when the economic limit instant gasoline ratio is reached, the net present value istaken as screening basis, and the method and process of screening the space and considering geological conditions, the development effect and economic benefits by adopting the SAGD optimal well are formed. By adopting the method, quick screening for the space of a target area block by adopting the SAGD optimal development well can be achieved under the condition of different gasoline prices.