Distributed generating technology has been widely used in smart grid. A new sufficient criterion protection strategy is proposed to solve the protection problems in distributed generating smart grid. The largest difference between sufficient criterion protection and traditional ones is that it is based on the selected representative fault characteristic which is widely seen in almost every actual fault condition, yet not lay equal strength on those theoretically might happen but hardly seen ones. Traditional protection theory emphases selectivity on any theoretically fault, thus requires rigid prerequisite, such as the communication and synchronization requirements. On contrast, the new sufficient criterion protection is more practicable. In this paper, a sufficient criterion of fault current amplitude characteristic is analyzed, and then a new protection method is proposed based on this sufficient criterion. Simulation shows the new strategy is more adaptable in distributed generating smart grid, and more reliable than traditional protection strategy.