This paper concludes that the formation of loess is in fact a result of soil-forming.Loess in the different regions such as steppe,desert steppe and forest steppe regions,may develop into Isohumisols,Aridisols,Cambisols,etc.But compared with reddish paleosols,it was formed in dry and cold conditions,so,loess even could serve as an indicator of dry and cold climate.The evolution of loess occured with change in the post-weathering,post-soil-formation and post-lithfication after aeolian deposit.