To comprehensively evaluate the safety of large grounding connection, testing and action principle of the main factors that impact the safe operation of grounding connection, were analyzed and studied, and the following conclusions were drew by theoretical analysis and simulation research. While evaluating step voltage and touch voltage, it's inadvisable to consider seasonal factors during the selection of soil resistivity; the testing direction of step voltage and touch voltage should be selected based on simulation computation for getting reliable data; eligibility criterion on electric integrity of grounding connection should not be 200mΩ but appropriately lowered; corrosion evaluation of grounding connection can be get rudely by analogized ways, which need the adding appropriate monitoring point in the corner of the grounding grid. Finally, the grading criterion and reference methods of weight value for the testing results of safe operation factors of grounding connection is proposed for establishing a quantified evaluation system of grading grounding connection, detailing the state evaluation system of large grounding connection.