The characteristics of radio frequency atmospheric pressure discharge in nitrogen and oxygen mixture gases are investigated by using a one-dimensional fluid model.The model consists of equations of particle continuity,Poissons equation,and the electron energy equation.The effect of the concentrations of O2 in N2 on the discharge characteristics is analyzed.The results show that when the concentration of O2 in N2 is less than 12％,as the amount of O2 grows,the electron density and the N+4 ion density decrease;the main negative particles are electrons.When the concentration of O2 in N2 is greater than 12％,the electron density and the N4+ ion density increase with the increasing admixture of oxygen;the main negative particle is the O-ion.Moreover,the O-ion density,the O+2 ion density,the electron temperature and the mixture gases electronegativity increase withgrowth of O2 in the range from 4％ to 20％ and with density of O2 in N2.