The aim of this paper is to analyze the relation between the reaction rate coefficients, hence the production of active species, and the gas mixing ratio in a comparative way between Ar/N2 and He/N2 gaseous mixtures. The Ar and He contributions were from 0 to 100 % at total gas pressure of 0.4 Torr and reduced electric field E/N of 610 Td. Langmuir probe is employed to measure electron temperature. The results showed that, adding Ar to N2 plasma reduced both the discharge operating voltage and the electron temperature. However an opposite action is obtained on Adding He. Also, Ar can induce the dissociation of molecular nitrogen and increase the production of nitrogen atoms however; it has insignificant effect on the nitrogen ionization mechanism. On the other hand He addition enhances the production of N_2^+, N+ and N-atoms through ionization, ionization dissociation and dissociative reaction however it has a decreasing effect on the dissociative recombination mechanism.