Abstract: The not well designed grounding system of electrically power equipment in primary processing line resulted in significant mutual disturbance,the leakage current in PE line was above 300 mA.During production,the alarm of communication failure between PLC and frequency converter occurred frequently,the efficiency of equipment was influenced.The grounding system was improved as following:1) installing an isolation transformer of 380 V/220 V to supply power of 220 V;2) separating protective grounding and shield grounding completely;3) changing the way of protective grounding in main control panel.After that,the ability of control system against electromagnetic disturbance was improved,and the alarm caused by disturbance decreased obviously.