The pitching rotation of a telescope will cause the relative displacement between a primary mirror and its cell, and the displacement will influence on the stabilizing image of a telescope. To correct the relative displacement of the primary mirror, a method for stabilizing images of the primary mirror was proposed based on a hydraulic support to control the displacement between primary mirror and cell. A 1.23 m SiC mirror in our lab was used to complete the online measuring experiment and a mirror position measuring system with 6 Line Variable Differential Transformer(LVDT) was established. Under two cases with or without mage stabilizing technologies based on hydraulic support, the displacement between mirror and cell was measured, and the 5 freedom of mirror was computed by using the measured data from sensors. Experimental results indicate that the proposed technology based on hydraulic support has excellent stabilizing image ability. Under the case without the image stabilization technology, the mirror displacement of Z direction is about 150 μm and the angle around X axis is 2.5″ when the rotation angle of mirror is 40°. However, the X displacement has reduced to 3 μm and the angle reduced to 0.4″ when this technology is conducted. It concludes that the stabilizing image technology based on hydraulic support can implement the determination and control of primary mirror position in real time.