We present a new, to the best of our knowledge, simulation method for laser-induced breakdown spectroscopy during the plasma expansion phase in nonlocal thermodynamic equilibrium. Our method uses the particle-in-cell/Monte Carlo collision model to calculate dynamic processes and line intensity of nonequilibrium laser-induced plasma (LIP) in the afterglow phase. The effects of ambient gas pressure and type on LIP evolution are investigated. This simulation provides an added way to understand the nonequilibrium processes in more detail than the current fluid and collision radiation models. Our simulation results are compared with experimental and SimulatedLIBS package results and show good agreement.