Abstract: Aimed at the problems that grids are more prone to failures, and existing failure detection algorithms can not satisfy the unique requirement of grids, a dynamic failure detection algorithms is presented. According to the characteristics of grids and unreliable failure detection theory, the authors establish models for grid systems and fault detection respectively; Combining heartbeat strategy with grey prediction method, they also design a dynamic heartbeat strategy, and present the prediction model, as well as a real-time prediction strategy. Furthermore, on the basis of the dynamic heartbeat strategy, a fault detection algorithm is put forward for grid environments, and its dependability is analyzed. Finally, simulation results shows that the algorithm is valid and effective, and can be used for fault detection under grid environments.