Adopting the plasma kinetic model, we perform a numerical calculation of evolution characteristics in N2/O2 plasma with various reduced electric fields. The results show that there is an approximate linear relation between electron average energy and reduced electric field, the electron average energy is 2.6 eV and its maximum is 35 eV when reduced electric field is 100 Td, and reduced electric field has a strong influence on electron energy distributing function. The number densities of nitrogen molecules and atoms, oxygen atoms in electronic excited state reach their peaks when discharge is over, then drop off; but the number density of nitrogen molecules in vibrational excitation remains unchanged after discharge; oxygen atoms recombine into ozone molecules. With the increase of reduced electric field, the number density of vibration excitated nitrogen molecules reduces because of the decrease of the number of electrons with low energy, but other particles are increasing. The number densities of vibrational excitated nitrogen molecules are 3.831011cm-3, 1.981011cm-3 and 1.771011 cm-3 when reduced electric fields are set to be 50 Td, 75 Td and 100 Td respectively.