This article presents a simple alternative procedure for evaluating the structure of InGaAs/InGaAs strained layer superlattices (SLSs) by x‐ray diffraction measurements. A symmetric reflection configuration is adopted for the scanning mode of (hkl) reflection measurement contrasting to the commonly used asymmetric configuration for SLS. In order to determine the average lattice constants for the SLS under the scanning mode, an analytical formula is derived with respect to the symmetric reflection configuration. A new discrimination method of the fundamental peak is also proposed in which a simple experimental method is useful especially for the SLS case because the fundamental peak is usually not the most intense. This method works also as a simple criterion of coherent lattice deformation. The analytical procedure is applied to the evaluation of InGaAs/InGaAs SLS structures. The lattice deformation and composition of well and barrier layers are estimated by parameter fitting to the satellite peak intensity profile based on the obtained average lattice constant. The results reveal that the sample is coherently deformed as designed.