The invention relates to the technical field of diesel engine fault detection, and particularly relates to a diesel engine fault detection device. The diesel engine fault detection device comprises a data acquisition module, a data storage module, a fault detection module and a fault alarming module, wherein the data acquisition module is used for acquiring performance parameters of the diesel engine; the data storage module carries out operation, management, maintenance, storage and query on all data in the detection system; the fault detection module is used for judging whether the diesel engine operates normally; the fault alarming module displays the fault and gives an alarm; and the modules communicate through a CAN bus. The data acquisition module is used for acquiring data indexes when the diesel engine operates, the detected data are transmitted to the data storage module through the CAN bus, the fault detection module analyzes the acquired data and the data in the data storage module, the fault is detected, and the alarming module gives an alarm.