Abstract: A method is presented to derive the structure for a quasiparabolic ionospheric layer from the curve of minimum time deley of a sweep-frequency HF backscatter without any requirement of other parameters.Provided that there is a relation between the maximum hight and se-mithickness of the layer,the data of only two points are needed for the inversion.The method is illustrated with some numerical examples.The use of the method in the practice is discussed.