Axial plunger pump is considered as the core component of hydraulic system, and its performance directly determines the safety and reliability. The complicated symptoms, such as pressure pulsation, substandard flow rate, large amount of oil leakage, abnormal shell vibration and so on caused by the faults of three friction pairs and bearing can improved the difficulties of accurately identifying the source of the faults for the researcher. However, the abnormal vibration timefrequency curve of the shell in the different fault modes of axial plunger pump is inconsistent. Therefore, this paper analyzes the generation mechanism and transfer law of fluid vibration in the normal and various fault modes of axial plunger pump. The fluid vibration transfer path model and vibration differential equation of axial plunger pump are established. The vibration response curves in time/frequency domain of the front, middle and rear shell under various modes are presented by MATLAB, and typical fault characteristic signals are extracted. This paper provides theoretical basis for diagnosis of axial plunger pump in various fault modes.