Abstract: The synchronous condenser (SC) can provide transient reactive power support for the ultra-high voltage direct current (UHVDC) converter station in system fault, keep voltage stability and prevent commutation failure. However, high reactive power output leads to the temperature rise of the SC and limits its transient operation ability. The initial condition before the fault has an important impact on the transient temperature rise and operation ability of the SC. In order to study the relationship between the transient temperature rise and the initial condition, the electromagnetic field and temperature field of the SC are coupled with the grid model, and the stator and rotor losses and temperature of the SC under different steady-state operating conditions are calculated. Taking the single-phase short-circuit fault as an example, the influence of the initial condition of the SC on the transient temperature rise is studied. The variation law of single-phase short-circuit duration of the SC with initial condition is revealed based on the maximum withstand temperature of each component. The research provides the technical support for improving the transient operation ability of the SC under low system voltage.