The relation of oxygen incorporation of RuO2 lm and Li+ ions is not clear as yet. To nd a correlation between the capacitance and oxygen contents can provide the insight of mechanism and the improvement of performance. We sputtered the bottom electrode, RuO2 lm on Pt/TiO2/Si substrate in di erent oxygen partial pressure. Lipon (lithium phosphorous oxynitride) lm as an electrolyte was r.f. sputtered on it, and RuO2 lm as a top electrode was deposited on Lipon with the same procedure of the rst layer. In this work, we studied the e ect of oxygen excess on the performance of TFSC. All solid-state TFSC was tested with charge-discharge cyclic measurement. It ran for 200 cycles. As the cycles go on, the capacitance decreases gradually. When oxygen partial pressure increased during RuO2 lm deposition, the fade of capacitance rised.