Abstract: Rock brittleness is one of the key parameters to be considered in the exploration and development of unconventional oil and gas reservoirs. The Young's modulus and Poisson's ratio method based on rock elastic parameters of normalized is currently widely used for seismic prediction of brittle rock evaluation technology, but the results could be severity affected by parameters of normalized. The Young's modulus and Poisson's ratio as the evaluation index of brittleness, and the scale of large quantity of rock mechanics experiment, has increased the reliability of brittle rock discrimination, this paper re-division of brittle category, focusing on analyzing the effects of minerals and rocks on the brittle zone, and explore the brittleness index calculation method and formula, to play a reference role for the number of period of J depression Permian Lucaogou Formation compact rock brittle prediction.