Insulation detection is a key link to ensure the electrical safety of Electrochemical Energy Storage System (EESS), but when the Power Conversion System (PCS) operates with a low-resistance circuit conduction between the AC side and the DC side, the problem of false alarms of insulation detection occurs, which seriously affects the stable operation and fault judgment of EESS. This will seriously affect the stable operation and fault judgment of EESS. In this paper, we analyze the formation mechanism of the low-resistance circuit in EESS, search for the reasons why the current insulation detection method is prone to false alarms, and propose an insulation detection false alarm suppression method based on active floating-ground switching, which is validated by simulation and experiment. The experimental data show that under the active floating ground switching strategy, alarm accuracy increased to 98.7%, and the detection response time is shortened to less than 200ms. The active floating-ground switching strategy can significantly improve the accuracy of insulation detection, which is of great significance for improving the intelligence level and operational reliability of ESS.