By experiment methods of DTA,XRD,SEM and MIP,the influence of the ferrite on the hydration products of barium-bearing calcium sulfo-aluminate was studied.The results show that the main hydration products are BaSO_4,Fe-bearing C_3AH_6,CAH_(10) or C_2AH_8,Fe(OH)_3 gel and(Ca(OH)_2) gel.When C_(2.75)B_(1.25)A_(2.75)Fe_(0.25) hydrates,transition of the unstable Fe-bearing CAH_(10) and Fe-bearing C_2AH_8 are held back by a little Fe~(3 ) ions,but the transition are promoted by a great lot Fe~(3 ) ions and leads to the reduction of late strength.