With the development of UHV AC/DC transmission, synchronous condenser has been paid more and more attention because of its fast dynamic response ability. The safe operation of synchronous condenser is related to the stability of power grid. Taking TTS-300-2 dual water cooled synchronous condenser as the research object, and a three-dimensional model of its rotor is established. The three-dimensional temperature field of the rotor is calculated and analyzed under different loads and degrees of water blockage at the same position. The temperature field of the rotor with interturn short circuit fault and water blockage fault are calculated and analyzed. The thermal stress of the rotor with water blockage fault is also studied. Based on the analysis, the impacts of these faults and the ability of the synchronous condenser to operate are evaluated. The results show that the distribution of rotor temperature field is similar under different loads. Rotor fault leads to unbalanced temperature distribution. The more turns of blockage in a single slot, the more obvious temperature distortion of the rotor. The thermal stress of rotor increases with blockage degree.