A calculation system of fault coverage includes a data acquiring module acquiring layout information and gate net data, a layout analysis and fault link module extracting a layout element information and generating a undetected fault list, a fault detecting module generating a detected and undetected fault list, and a weight calculating module adding layout element information as weight, based on a link file between faults and layout element information to be generated based on the layout information, the gate net data, and the detected and undetected fault list.