A model on formation of the vibrational distribution function of metastable electronically excited N2(A3S ,v) states in nitrogen discharge plasma is presented. It is assumed that the probability of population of N2(A3S ,v) states by collisional deactivation of N2(B3Пg,v') molecules is proportional to the Franck-Condon factors of corresponding N2(B3Пg,v') --> N2(A3S ,v) transitions, i.e. that the quenching is essentially vertical. The results of calculations carried out under this assumption are in agreement with measured N2(A3S ,v) vibrational distribution at the end of pulsed high current discharge in nitrogen.