The invention discloses a method for predicting the complexity of a fracture network formed by shale fracturing, and the method comprises the steps: S1, determining the percentage contents of variousminerals, including quartz, orthoclase, plagioclase, pyrite, calcite, dolomite and other substances, of a shale core; s2, then determining the standard quantity to be 16.7% by utilizing the variety ofbrittle minerals; s3, recalculating the percentage contents of various brittle mineral components by only considering the brittle minerals; s4, determining a phase difference k by utilizing the standard quantity and the newly determined mineral percentage content; s5, calculating the brittleness B of the brittle mineral; and S6, finally, the brittleness index BI is determined by combining other minerals, and the larger the brittleness index BI value is, the larger the number of cracks is, and the more complex the fracture network formed through fracturing is. The invention provides a novel prediction method for the complexity of a fracture network formed by shale fracturing.