The　present　study　investigates　the　effects　of　rare　earth　and　aluminium　on　the　microstructures　of　as　cast　and　heat　treated　semisolid　Fe-B　cast　alloys.　The　as　cast　microstructure　of　the　semisolid　modified　Fe-B　cast　alloy　consists　of　the　eutectic　boride,　pearlite　and　ferrite.　Moreover,　compared　to　a　net-like　distribution　of　the　coarse　eutectic　borides　in　the　ordinary　unmodified　alloy,　the　eutectic　boride　structures　in　the　semisolid　modified　alloy　are　greatly　refined　and　less　interconnected.　After　heat　treatment,　the　phases　in　the　semisolid　modified　Fe-B　cast　alloy　consist　of　the　boride　and　martensite.　The　additions　of　rare　earth　and　aluminium　help　to　promote　the　formation　of　the　short　rod　shaped　and　round　borides　in　the　semisolid　Fe-B　cast　alloy　during　heat　treatment.　Compared　to　the　ordinary　unmodified　alloy,　there　is　no　significant　change　in　the　boride　area　fraction　but　an　obvious　decrease　in　average　boride　area　in　the　semisolid　modified　alloy.