The invention relates to an intelligent power grid safety technology, in particular to an error data injection attack defense method based on PMU deployment in an intelligent power grid. The method comprises three stages of a new low-overhead hybrid attack mechanism, PMU pre-deployment of fragile nodes and PMU-based greedy strategy deployment of the whole network. In a stage of a new low-overheadhybrid attack mechanism, an attacker can attack a bus with low smart grid connectivity with low overhead to cause an error state estimation result. In a PMU pre-deployment stage of a fragile node, firstly, a bus which is most easily attacked is protected through PMU deployment. And in a PMU greedy strategy-based deployment stage of the whole network, according to the current attack vector, a PMU device is deployed on a bus capable of protecting the maximum number of measurement values in each round of deployment until the whole power grid is completely observable. According to the defense method provided by the invention, the attack overhead of an attacker is increased, and the deployment iteration process is reduced; after deployment is completed, effective defense of an error data injection attack is realized.