Calcined powders with the composition of Sr1-xLaxFe2n-xCoxOα (x=0-0.4) were investigated. The addition amount of Si or Ca oxide and combinations thereof were varied to analyze the effects on microstructure and magnetic properties of the calcined powders. It has been proved that there are interactions between the addition amount of Si-Ca oxide and La-Co oxide; what’s more, the right amount of Si-Ca additives can optimize the performance of the La-Co substituted calcined powders.