Abstract: The inflection points are very important for chemical structure graphs. If the inflection points of chemical structures could be discriminant effectively, they would make the effectiveness of the extraction of chemical bond information improved greatly. The characteristics of the chemical structure was analyzed and summarized, and the advantages and disadvantages of the Hough method was balanced. It was found that the offset value of the edge points was with strong regularity,which played an important role on the extraction of the inflection points and the judgment of chemical bond type. Finally, the experiments selected 100 BMP figures of the molecular structure to extract and count the chemical bond information. The statistic results showed that the accuracy rate of chemical bonds information extraction was of 7383％， which proved the effectiveness of this method.

Key words: chemical structure graphs, chemical bonds, the line segments extraction, inflection points