An automatic system for evaluating single cell viscoelasticity is proposed and tested in this paper. The system includes three main operations, and they are the operations of catch, load and launch. In the catch operation, the system is capable of capturing a target cell by high-speed vision and high-frequency flow control. The captured cell is pushed into a narrow constriction for the load operation. Different durations of loading time are applied to cells for evaluating cell viscoelasticity. Finally, the cell is launched out from the constriction, and the recovery response of the cell is monitored for cell characterization. Human red blood cells are experimentally tested by the proposed system. The experimental results show that the system successfully perform the evaluation, and the viscoelastic characteristics of the cells are discussed.