Abstract: Derivatives obtained by chemical modification of compounds or halogen salts formed by recrystallization were used to procure single crystals for X-ray diffractio( XRD).Thechemical modification would lead to some fine stereo-structural changes.Through XRD of crystal structure of five natural organic molecules,their average deviation value(Δ)for bond length ,bond angle and torsion angle were obtained.We have also calculated the salt bond value in ten crystal structures of halogen salts(HCI ,HBr)and obtained their average deviation values.The average deviation value for fine stereo-structure parameters constitutes a standard value to describe the stereo-structure changes.