Microporosities in casting alloys cannot be avoided in the casting process. They will destroy the continuity of matrix, cause stress concentration, become the crack source of fatigue failure, and reduce the fatigue life of structure greatly. The current progress of microprosity characteristics (size, shape and position) in casting alloys and their effects on fatigue life is reviewed and prospected in this paper. Most of the microporosities are casting porosities with irregular shape and rough inner wall, and they have great influence on fatigue life of casting alloy. The size characteristic of microporosities well follows the lognormal distribution and the maximum size can be a typical feature to evaluate the fatigue life. And shape characteristics follows the Weibull distribution, however the position characteristics is complex. It is hard to observe the maximum size porosity in large-size casings, so the statistical methods are always used to predict them, and the generalized Pareto distribution method can get the best prediction results. At present, the fatigue life prediction methods of casings with microporosities are not complete and the failure mechanism of microporosity is not clear, the quantitative prediction model of fatigue life needs to be further studied, which considers different characteristic parameters of porosities and the interaction between different porosities under complex loading.