The active deformable reflector is a significant technological innovation that distinguishes the FAST from traditional radio telescopes. Those hydraulic actuators receive instructions from the control room to flexibly adjust the position of 4,450 reflection units to achieve a specified position for observation.

During astronomical observations, it is difficult for naked eyes to see the deformations — tiny changes of the huge reflector from the surface — but the noise of thousands of hydraulic actuators roaring together can be heard. Because of their heavy workload, the hydraulic actuators get the most care and maintenance.