A transient stability model based on back propogation neural network is used to analyse transient stability of java-bali electricity system, especially in calculating the critical clearing time. Inputs used for the neural network is the real and the active variable load power, whereas the target of the neural network is the critical clearing time (CCT). Data of target CCT used for the training was calculated using the concept of One Machine Infinite Bus (OMIB), which is the reducation of multi-machine system in combination with the method of equal area criterion (EAC) through the trapezoid method and the 4 th order runge-kutta method. The position and type of 500 kv Java-Bali system with type of disturbance is 3 phase ground fault. The results indicate that the approximate value of the CC calculated by the proposed method has a minimum eror of 0% and maximum error of 0.0008% compared with CCT by OMIB. Keywords: transient stability, multimachine, one machine infinitive bus, equal area critarion, neural network