The Si content dependences of the magnetic properties of the Fe82.65Cu1.35SixB16-x alloys prepared by melt spinning were studied. The maximum Bs and minimum Hc were observed at around x=2 for the annealed Fe82.65Cu1.35SixB16-x alloys. The Bs and Hc of the annealed Fe82.65Cu1.35Si2B14 alloy were 1.84 T and 6.5 A/m, respectively. The average grain size of the bcc Fe nanocrystal in the annealed alloys with x≤2 was about 20 nm, it increased with x at x≫2. The annealing temperature range without the precipitation of o-Fe3B expanded with Si content.