The composition and function of turntable are described.The working principle of a bunch of par-allel light gathered on the focus when passing off-axis parabola was applied to design a test system to adjust the internal optical alignment precision for the turntable.The test equipment was used to directly observe the spot displacement，and to make a position adjustment of a few slices of mirrors to reach the target accuracy.In order to reduce the test error of test system，the off-axis parabola on the focal plane of the defocus amount was strictly controlled，and the potential error of the system was analyzed.