An instrumented drilling system can be applied for the acquisition of drilling process parameters. The system can provide continuous and huge data for geotechnical engineering. However,due to the complexity of ground strata,the variation in the drilling parameters with stratigraphical characteristics is great and the correlation between likely comparable parameters is not high,which limits the use of conventional correlation approaches in this field. How to use the data for engineering and how to get a reasonable interpretation for the relationships among the drilling parameters,as well as between a drilling parameter and formational characteristics,become a technical choke point for the development and application of the instrumented drilling system. Based on similarity criteria,the extraction of sample data and characteristics,the pretreatment of data and feature matching algorithms have been analyzed and an approach of slope coefficient searching identification has been established. A case study was carried out for the similarity between the rotational speed of the drill bit,flushing pressure,and effective thrust force graphics in general weathered granite. The result shows that the similarity coefficients between the rotational speed of the drill bit,flushing pressure,and effective thrust force are 0.72 and 0.83,respectively. Although there are differences between the distances of the graphics,the curves of both rotational speed and flushing pressure agree with the effective thrust curve in shape,which provides a possible method for the identification of various formations by use of the similarity between feature drilling parameters. The system can provide continuous and huge data for geotechnical engineering. However, due to the complexity of ground strata, the variation in drilling parameters with stratigraphical characteristics is great and the correlation between likely comparable parameters is not high, which limits the use the conventional correlation approaches in this field. How to use the data for engineering and how to get a reasonable interpretation for the relationships among the drilling parameters, as well as between a drilling parameter based on similarity criteria, the extraction of sample data and characteristics, the pretreatment of data and feature matching algorithms have been analyzed and an approach of slope coefficient searching identification has been established. A case study was carried out for the similarity between the rotational speed of the drill bit, flushing pressure, and effective thrust force graphics in general weathered granite. The result shows that the similarity coefficients between the rotational speed of the drill bit, flushing pressure, and effective thrust force are 0.72 and 0.83, respectively. Although there are differences between the distances of the graphics, the curves of both rotational speed and flushing pressure agree with the effective thrust curve in shape, which provides a possible method for the identification of various formations by use of the similarity between feature drilling parameters.