The calculation of aerodynamic force and aerodynamic heating for flight vehicles round trip to Earth's atmosphere （over different flow regimes） is one of the challenges and hotspots in computational fluid dynamics. Since the flow scenarios faced by such vehicles are no longer purely continuous flow or rarefied flow， neither the Navier-Stokes equations’ solver nor the direct simulation Monte Carlo （DSMC） method can obtain accurate results. In recent years， based on the Boltzmann model equation， which is independent of the continuity hypothesis， various numerical approaches have been developed to simulate fluid flow problems in all flow regimes by discretizing this equation in both physical space and velocity space. This paper reviews and analyzes the research progress of this kind of algorithm， including the gas kinetic unified algorithm （GKUA）， the unified gas kinetic scheme （UGKS） and the improved discrete velocity method （IDVM）. It focuses on the basic ideas and the implementation of these methods and pays attention to their current progress and applications. At the same time， the IDVM is further extended to simulate the unsteady flows in all flow regimes. Finally， some problems existing in this kind of algorithm are discussed and the prospect for work in the future is proposed.