A state-to-state model is used to simulate thermochemical nonequilibrium nozzle flow of N₂/N mixture. Quasi-onedimensional nozzle flow at reservoir temperature from 3 000 K to 8 000 K and pressure from 1 atm to 10 atm is simulated numerically to obtain flow properties,especially detail vibrational population distribution. Evolution of macro- and micro-properties of nonequilbrium flow during expanding is analyzed. Rationality of two-temperature or multi-temperature approach is investigated for recombination dominating flows.