The stator end magnetic shield of the synchronous condenser (SC) can reduce the losses of the end core and structural components, but it also changes the permeability of the end magnetic circuit and the stator end leakage reactance, further affecting the transient reactive power characteristics of the SC. In order to study the influence of the magnetic shield on the leakage magnetic field and leakage reactance in the stator end region, the three-dimensional end electromagnetic field model of the SC is established. The distribution of magnetic flux density and energy density in the stator end region under different magnetic shield thicknesses is calculated, and the variation law of the stator leakage reactance along with the increase of the magnetic shield thickness is revealed. On this basis, the influence of typical operating conditions of the SC, such as normal excitation, overexcitation and underexcitation, on the stator end leakage reactance is studied by combining the frozen permeability method (FPM) with the energy method. The variation law of the stator end leakage reactance along with the operating condition and magnetic shield thickness is revealed by analyzing the effect of the magnetic shield thickness on the end magnetic field and its energy under different operating conditions. The results show that the differences of the stator end loss and end leakage reactance are small when the magnetic shield thickness varies from 45 mm to 60 mm, thereby the magnetic shield thickness of 45 mm is optimal. The research results can provide a basis for selection of the magnetic shield thickness in the end region of the SC.