Abstract: Determine reasonab1e pore pressure tendency is a key to detect pore pressure using a convential dc exponent method. Analyzing tendency equation of dc exponent utilizing mathematical statistic’s method, the tendency lines has a similarly slop and different intercepts in same structural zone. The characters of tendency equation and dc exponent have been discussed and the concept of dc exponent has been further analyzed. It is believe that analyzed results will be help to detect pore pressure.