The invention provides a preparation method of an Nb-based amorphous alloy and a stripe and a hydrogen permeating metal film of the Nb-based amorphous alloy, According to the preparation method, the Nb-based amorphous alloy has the chemical formula as Nb0.42NiaCobZrcMd, wherein M=Ta, or Ti; a, b, c and d are respectively the atomic percentage of each component, wherein a is more than or equal to 0.30 and less than or equal to 0.40, b is more than or equal to 0.05 and less than or equal to 0.15, c is more than or equal to 0.04 and less than or equal to 0.02, d is more than or equal to 0 and less than or equal to 0.08, and the sum of a, b, c and d is equal to 0.58. With the adoption of the preparation method provided by the invention, the alloy components are further improved; the hydrogen permeating performance and thermal stability of the Nb-based amorphous alloy stripe and the hydrogen permeating metal film are improved; the Nb-based amorphous alloy capable of separating hydrogen and purifying is prepared, and the Nb-based amorphous alloy stripe and the hydrogen permeating metal film which have high performance of hydrogen permeating and are capable of separating and hydrogen and purifying can be obtained.