Abstract: Theoretical screening analysis on external loads of the external arm-type turntable, finite element simulation analysis and experimental research on bearing performance are carried out. A finite element model considering contact nonlinearity is established, and the high confidence and calculation accuracy of the finite element analysis method are verified by comparison with experimental test results. The results show that under the constant external load of the turntable, the bearing load of support arms, structural stress and deformation are all changed in a sinusoidal pattern with loading angles. Under the most severe working conditions of simulation, the maximum structural stress is set as 553 MPa, the strength safety factor is set as 1.8; the maximum deformation is set as 7.47 mm, and the angular deviation of rotation center is set as 21 arcseconds, which is superior to the design index requirement of 36 arcseconds. A mechanical test method suitable for large turntables under multiple loading angle working conditions is proposed, and the supporting test device is designed. The mechanical responses under the most severe working conditions obtained from tests are highly consistent with simulation results: the measured maximum deformation is obtained as 7.89 mm, with a relative deviation of 5.3% from the corresponding simulation measuring points; the measured maximum stress is obtained as 202 MPa, with a relative deviation of 5.4% from the corresponding simulation measuring points; the linear correlation coefficient between deformation and load is specified to be no less than 0.99; the maximum relative deviation between simulation stress and all test measuring points with stress greater than 30 MPa is calculated as 6.7%, which indicates that high consistency is maintained between simulation and experimental results. The maximum structural stress in regions unavailable for experimental measurement is estimated to be about 572–654 MPa by calculation based on the upper limit of relative deviation, and the safety factor is controlled to be greater than 1.5.