Spectrometry is used in the present work to analyze the characteristics of plasma which is formed during the discharge of a gas mixture. The work was performed on a needle plate electrode arrangement with an SF

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concentration ratio from 20% to 80%

a pressure range between 0.1 MPa to 0.3 MPa

and electrode gap length from 4 mm to 10

mm. A multiline slope method and Stark broadening method are used to calculate parameters such as electron temperature and electron number density in the conductive channel of the discharge when the SF

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/CF

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mixture is completely broke down. The relationship between the parameters and gas pressure as well as electrode gap length is established. The study shows that when the electrode spacing is 4 mm

with the rise of mixed gas pressure

the electron temperature of the plasma will decline but the electron number density of plasma will rise. The electron temperature in the plasma channel will decrease from 3.72 ×104K to 1.99 ×104K and the electron number density will increase from 2.61×1017m-3to 5.72×1017m-3under the condition of 80% SF

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（mass concentration）with pressure from 0.1 MPa to 0.3 MPa. With a pressure of 0.1 MPa and electrode spacing is 4 mm

the electron temperature in the plasma channel will rise and the electron number density will decline as SF

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gas content increases. When the electrode spacing is between 4 mm to 10 mm

ρSF

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is 20% and the pressure is 0.1 MPa

the electron temperature and the electron number density in the plasma channel are basically unchanged. Theelectron temperature is about 2.35×104K and the electron number density is about 3.22×1017m-3.