The influence of partial replacement of Fe by Mo element on thermal stability and soft magnetic properties of the Fe–Nb–B amorphous alloys was investigated in detail. The results indicated that the crystallization behavior is dependent on the Mo content. It undergoes two-stage crystallization events for the alloys containing 1 at.% Mo and 3 at.% Mo, while it undergoes only single crystallization event for the alloys containing 5 at.% Mo. The addition of Mo element is benefit to increase the glass transition temperature Tg and onset crystallization temperature Tx1. As the Mo content increases, the thermal stability is enhanced and the glass forming ability (GFA) decreases slightly. The Fe70Nb6B23Mo1 alloy is found to reveal the largest GFA with low the glass transition temperature Tg (=830 K) and wide supercooled liquid region ΔTx (=53 K), which agrees well with that predicted by thermodynamic parameter PHS. The Fe71-xNb6B23Mox (x=1, 3, 5) amorphous ribbons show good soft magnetic properties with high saturation magnetization (Ms) and low coercivity (Hc), and the Ms value is in the range 60–84 emu/g. The Fe71-xNb6B23Mox (x=1, 3, 5) amorphous alloys exhibit a correspondence between thermal stability and soft magnetic properties.