Fault characteristics analysis is precondition of relay protection. Theoretical derivation of permanent magnet synchronous generator (PMSG) fault current is necessary. In accordance with the theory that grid-side converter of PMSG is a power balance system under control action, an electromagnetic transient model of PMSG was proposed. Based on it, the active and reactive current was deduced and then the expression of three-phase fault current was obtained and its components, frequency, and attenuation speed of every component and other characteristics were analysed comprehensively. Simulation on PSCAD and field fault recording data as practical analysis verifies that the expressions and the characteristics are correct. The results of this paper are not only important to relay protection, but also are references to transient calculation and transient modelling.