This paper used Direct Simulation Monte Carlo method(DSMC) with structured grid to simulate the flow and heat transfer in the vacuum-jacket of a parabolic trough collectors(PTC).Heat absorption by the heat transfer fluid(HTF) in the absorber tube and heat loss by the wind outside the glass tube were coupled calculation.The numerical results were compared with experimental data and consistent with good,proving that the model and method used in this study were feasible and reliable.