The non-linear behaviour for wearing fault of reciprocating membrane pump was investigated with chaos theory and fractal technology. The vibration acceleration signals of the wearing in different joint were collected to analyse. Poincare sections were drew to study the status of the system. Correlation dimension and the largest Lyapunov exponent were calculated to recognize the different wearing. The results showed that non-abrasion pump system is in quasi-period state, while the fault status is in chaos. The research also indicated that different wearing fault has different largest Lyapunov exponent and different correlation dimension, which can be used as the characteristics for the pump’s monitoring and fault diagnosis.