The invention belongs to the technical field of assessment of operation level and power supply capacity of power supply networks and particularly relates to a method for assessing operation level and power supply capacity based on a large-scale enterprise power supply network. The method comprises the steps of A, determining an assessment range; B, collecting, validating and assessing basic data; C, exporting single assessment index data; D, calculating the score of the single assessment index; E, obtaining scores of the operation level and the power supply capacity; and F, analyzing an assessment result. The method is suitable for assessment of the operation level and the power supply capacity of the large-scale enterprise power supply network, can reflect the current situation of the enterprise power supply network directly and quantificationally, and provides a reliable and practical assessment method for enterprise decision makers to carry power supply network system improvement and special control and to formulate and program decisions. Besides, the power supply network construction and project reconstruction can be arranged scientifically, reasonably and effectively according to the assessment method in actual assessment and planning work, and great economic benefits are brought for investment of power supply optimization performed by enterprises.