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首先，综述了根据分子运动论对连续介质极限气体行为的最近研究．它表明：经典的连续气体动力学是不完整的；用分子运动论分析在连续介质极限时一些重要情况得到气体的正确行为是必不可免的．即，除了特殊的情况，甚至在平均自由程变为零的极限下热传导方程不能描述静止气体温度场；文中给出了根据分子运动论导出的温度场的正确方程组和边界条件及其具体应用．还用同轴圆筒间的包含气体凝聚相的气体流场的渐近分析，论证了经典连续气体动力学方程组的不完整性．其次，综述了最近几年发现的稀薄气体流动的新特性．如在凸体周围速度分布函数的不连续性及它与Ｓ层的关系，加热平板边缘周围引起的流动，有周期性温度分布的管道内产生的单方向流动．
First, the recent research on the behavior of the limit gas in continuous media based on molecular kinematics is reviewed. It shows that the classical continuous gas dynamics is incomplete, and it is inevitable to use molecular kinematics to analyze the gas behavior in some important situations when the continuum limit is reached. That is, except in special cases, the heat conduction equation can not describe the temperature field of stationary gas even under the limit that the average free path becomes zero. The correct equations and boundary conditions of the temperature field derived from the theory of molecular motion are given, and their applications . The asymptotic analysis of the gas flow field containing the gas-condensed phase between coaxial cylinders is also used to demonstrate the incompleteness of classical continuous gas-dynamic equations. Secondly, the new characteristics of rarefied gas flow discovered in recent years are summarized. Such as the discontinuity of the velocity distribution function around the convex body and its relationship with the S-layer, the flow caused by heating the edge of the plate, and the unidirectional flow generated in the pipe with the periodic temperature distribution.