Shale brittleness is one of the most important evaluation factors in shale oil and gas exploration and development. For shale brittleness, the rock mechanics experiment is the main way at present，however, in this paper, we developed a new method of X-ray element logging technique to evaluate in element level. Based on the element composition and correlation between element and mineral, it is revealed that the Si, Ca, Mg element can reflect the content of quartz, calcite and dolomite respectively, which establishes the theory of evaluating shale brittleness by means of X-ray element logging. By means of appropriate method to calculate the silica index, carbonate index and brittleness index to reflect the content of rigidity mineral, we can realize the shale brittleness evaluation while drilling. In accordance with the shale petrology of Shengli oilfield and shale brittleness evaluation standards, the carbonate index is selected to evaluate the shale brittleness so as to establish the four class criterion(CI ≥0.6，high；0.4≤CI＜0.6，medium；0.2≤CI＜0.4，lower；CI＜0.2，low）. After application of this technique in well NY1 and L69 etc., we can provide logging approach to select the favorable shale in?tervals for fracturing.