Abstract: The L-type train on Guangzhou metro Line 4, Line 5 and Line 6 adopts the linear motor, the distance from the bottom of the linear motor to the sensor board is strictly required, because the sinking of linear motor will directly threaten the safe operation. In this paper, the possible causes of linear motor sinking are analyzed, such as the abnormal failures of pin shaft, motor height adjustment device, rubber joint, vertical suspender and other relevant parts, and relevant maintenance processes are formulated. Combined with case analysis, improvement measures and suggestions are proposed, including changing the motor height adjustment mode, improving the service life of rubber joint and metal joint, and strictly controlling the production quality of each part and the delivery inspection items.