Abstract: This paper presents a review of the characteristics and mechanisms of fatigue crack propagation（FCP）at near-threshold range in various metals and alloys.Experimental results from a series of microfractographic analysis of specimens and structures indicated that a type of crystallographic fracture,facets or river patterns,occurs predominantly at near-threshold range.A correlation of the orientation of facets for different metals and alloys with lattice structures,SFS and modes of slip was described.In this paper,the relation between the fatigue limits of plain-and notched-specimens and fatigue thresholds together with the mechanism of FCP behaviors in short cracks was evaluated.The crack propagation behaviors in short cracks can be generally expressed as,where f（a）is a function of the crack length and specimen geometry.The influence of stress ratio,microstructure and environment on fatigue crack propagation behaviors at near-threshold range was also reviewed.It is suggested that the concept of "oxide-induced" and "roughness-induced" crack closure may be useful for explaining the effect of the above mentioned factors on FCP behaviors at near-threshold level in structural materials.