The microstructure and soft magnetic properties of amorphous and nanocrystalline Fe65Co15Si5Nb3Cu1B11-xAlx (x=0, 1, 2, 3) alloys were investigated. Microstructure has been analyzed from XRD patterns and magnetic properties were mainly studied by the evolution of initial permeability (μi) from room temperature to 700°C. It was found that adding a certain amount of Al in Fe65Co15Si5Nb3Cu1B11 alloy significantly decreases onset primary crystallization temperature Tx1 from 452°C to 388°C and increases the crystallized interval temperature ΔTx from 188°C to 290°C. However, with the Al adding, the Curie temperature of amorphous phase Tcam shows a decline tendency. After annealing at 550°C, the alloy with x=1 exhibited the maximum room-temperature μi, however, the most stable soft magnetic properties at elevated temperatures was found in the alloy with x=3. Therefore, the (μi-T) curves of Fe65Co15Si5Nb3Cu1B8Al3 samples annealed at 520–580°C were also investigated in detail.