The paper presented an experimental study on air plasma, which was produced in atmospheric pressure discharge system with two needle electrodes, by using emission spectrum method. The emission spectrum consisted of continuous spectrum background and discrete spectrum above the background. The continuous spectrum resulted from bremsstrahlung and recombination emission in the plasma. The discrete spectrum were assigned to fluorescence emission of N2 C3∏u →B3∏g ,N+,N,O. The upper electron configurations corresponding to N+ fluorescence were 2s22p(2P0)3p and 2s22p(2P0)3d, respectively and their energy levels located between 20 eV and 23.6 eV. Time resolved spectroscopy of N2(336.8 nm), N+(500.5 nm), N+(399.7 nm) fluorescence signals were also acquired. The results show that N2(336.8 nm) fluorescence appeared firstly, then N+(500.5 nm,399.7 nm) fluorescence showed up at the same time with about 25 ns delay. Based on time resolved measurement and related references, the paper analyzed N+ production channels.