This paper presents a detail review offault diagnosis in rotating machinery. Pattern recognition technique which needs three main steps offault diagnosis - feature extraction, dimensionality reduction and fault classification - was used. This paper focuses on the faulty bearing which is mainly caused by mass imbalance and axis misalignment. By analyzing the vibration signal obtained from the test rigs (rigs that are built to demonstrate the effect offaults in rotating machinery), it gives solid information concerning any faults within the rotating machinery.