The effect of process parameters on the performance of silicon nano-sized etching in an Inductive-Coupled-Plasma Reactive-Ion-Etching (ICP-RIE) system is studied by the Taguchi experimental method. The Standard L9 orthogonal array is considered to evaluate the parameter effect and to obtain the optimum conditions. A total of 9 parameter settings are conducted to investigate the four parameters with three levels for each. The four parameters include the substrate temperature, bias power, gas cycle time and C4F8 gas flow rate. The source power and the SF6 gas flow rate are respectively fixed to a value of 500 W and 120 seem. The etching bottom roughness and the etching rate are the quality characteristics to evaluate the parameter effect. The results show that both the C4F8 flow rate and the bias power have the significant influence on the bottom roughness, while both the cycle time and the bias power play an important role on etching rate. And, the optimum conditions are obtained, of which the predicted quality has been confirmed by verification experiment.