According to the relative intensities of lines and transition parameters, through linear fit of linear function, two fit parameter are obtained. And by adopting these parameters, transition probabilities of spectral lines for special configuration or highly excited states can be calculated. In the present work, on the basis of spectroscopic analysis for N+ spectra, the transition probability whose upper states are pair coupling is obtained. The present work gives a simple and feasible new semi-classical method to calculate transition probabilities, especially for special configurations or highly excited states.