Abstract: In the geo-technical engineering investigation, a great deal of geo-technical testing and analysis should be carried out, and the testing results are reference to evaluate the engineering geological characteristic of different sites. However, some experimental results do not agree with the site characteristic in practice due to various factors. The reason that causes this unconformity should be analyzed and studied, while some problems must occure if only experimental results are used to evluate the engineering geological characteristic of a site. According to a case study, the experimental results of rock compressive strength were analyzed. The results showed that analysis on experimental data is important and instructive.