Abstract: Comprehensive brittleness indexes B_d1 and B_d2 including multi-parameters were proposed on the basis of the stress-strain curve. The brittleness characteristics were interpreted through the inflection point of dilatancy (the pre peak curve)， the residual strength (the post peak curve)， and energy analysis (the complete stress-strain curve). Axial and triaxial compression tests were conducted to examine the new indexes corresponding to failure mode. The results showed that the two evaluation indexes can preferably reflect the brittle characteristics of shale. For B_d1， related parameters can be selected freely according to different purpose， which can pay particular attention to any parameters in the process of brittleness evaluation. B_d1 can be better fitted by confining pressure with an exponential function. B_d2 can be used as a comprehensive evaluation index of brittleness evaluation， but B_d2 is not sensitive to high confining pressure. Under the coring angle of 90°， the evaluation indexes of brittleness decrease with the increase of confining pressure， and shale exhibits a tendency from brittle at low confining pressure to ductile at high confining pressure. The evaluation indexes are sensitive to confining pressure under low confining pressure and reduce quickly， and vice versa under high confining pressure.

Key words: shale, brittleness index, inflection point of dilatancy, residual strength, energy analysis, failure mode