Abstract: RF capacitive coupled plasma(CCP) was formulated with equivalent circuit model(ECM) based on the uniform ion density approximation,described with an energy balance equation and theoretically analyzed for CCP diagnosis.The results show that ECM works pretty well.To be specific,the sinusoidal I/V waveforms and a few high harmonic components,with an intensity<11%,co-existed in the ICP.An increase of discharge power increased the e-density,decreased the sheath width,widened the main plasma region,but little affected the e-temperature.As the pressure increased,e-density n_e and e-temperature T_e decreased.The e-density and e-temperatur,calculated with ECM and derived with plasma emission spectrum,were in good agreement. At a higher pressure,depending on the input power,the discharge could be in high-power γ-mode or low-power α-mode,simply because of Auger electron emission from the electrode.