It is quite difficult to quantitatively measure heat extraction in a fractured enhanced geothermal system (EGS) reservoir and its impacting factors. This study thus aims to define a characteristic parameter that is failure area percentage for evaluating and optimizing geothermal extraction. Through establishing a thermal-fluid-solid coupling model, the operation lifecycle and economy of an EGS case was evaluated by the proposed parameter. A sensitivity indicator was developed to measure the quantitatively effection of various factors on heat extraction. The results show that heat extraction increases with the three growing-up factors: fracture network complexity, pressure difference, and rock permeability. However, too large value of these factors are adverse to geothermal system smooth operation. Based on the sensitivity indicator analysis, heat extraction is the most sensitive to the variation of fracture network complexity. This study would provide a guidance for optimization of EGS designing. (C) 2021 Elsevier Ltd. All rights reserved.