The high temperature soft magnetic applications were mostly catered by CoFe-based crystalline alloys which revealed high Curie temperature more than 800K but inferior soft magnetic properties with coercivity ~150A/m. These alloys not only contained high content of expensive cobalt but also involved costly schedules of rolling into sheets and heat-treatment to get desired properties. The present invention particularly relates to a process for preparation of Co-Fe-Si-B-Nb based ferromagnetic alloys. The process involves preparation of range of master alloys with the general formula CoxFe72-xSiyB24-YNbz (Where 10 < x < 36, 1 < Y< 4, 1 < Z < 4 at %) by induction melting and then melts spinning of the master alloys directly into amorphous ribbons. The range of process parameters each relating to melting duration, melting temperatures, wheel speed of the melt spinner, ejection gas pressure of the alloy melt has been optimized to obtain 2mm to 30mm width of amorphous ribbons of 20µm to 6Oµm thickness. The range of heat treatment temperatures were optimized to get nanocrystalline state whereby the material showed high Curie temperature above 800K and soft magnetic properties with coercivity range as low as 14 A/m to 50A/m.