在直接模拟Monte Carlo(DSMC)方法的位置元方法中准确判断分子是否与某一表面元相撞 ,直接关系着气动力热的计算精度 ,是方法需要解决的关键问题。本文发展的分子表面反射判据 ,使这个问题得到了有效的解决。此外 ,还讨论了分子空间位置坐标的记录方法、分子碰撞对的极限距离、网格自适应等实际模拟技术。与圆球自由分子流准确解和过渡领域贴体网格DSMC模拟结果的比较 ,证明了上述判据和技术的有效性。 Accurately determining whether a molecule collides with a surface element in the position element method directly simulating a Monte Carlo (DSMC) method is directly related to the calculation accuracy of the aerodynamic heat, which is a key problem to be solved by the method. The molecular surface reflection criterion developed in this paper has effectively solved this problem. In addition, the methods of recording the position coordinates of molecular space, the limit distance of molecular collision pairs and the grid simulation are also discussed. Comparing with the DSMC simulation results of the exact molecular solution flow and the transition in the transition sphere, the above criterion and the validity of the technique are proved.