Abstract: Objective: In 2019, high voltage faults occurred frequently in the air conditioning system of Suzhou Metro Line 1 trains, resulting in a decrease of operational train number and an increase of passenger complaints. It is necessary to identify the cause of the faults and develop appropriate improvement measures. Method: Focusing on the common causes of high\|voltage faults in train air conditioning, preliminary investigations are carried out and some causes are ruled out. Combining the time, date, and location of 19 train air conditioning faults on Line 1 in 2019, the heat load, external temperature, and train operating environmental factors of the air conditioning unit faults are analyzed in\|depth. To identify the causes of the faults, optimization improvement measures are proposed. Result &Conclusion: The direct cause of the malfunction is poor air convection in local areas of the tunnel. The increase of the overall ambient temperature within the tunnel and decrease of the time required to exceed the threshold for high\|pressure switch action due to higher system pressure, results in a higher probability of high\|pressure failures. After considering feasibility and cost\|effectiveness comprehensively, two strategies are adopted: optimizing air conditioning control logic and controlling the duration of air conditioning activation when the train is parked at the storage line. After operational verification, these two strategies effectively prevented air conditioning high\|pressure failures caused by the loss of train airflow in certain locations along Line 1.