Nano-particles have several interesting properties which are not shown in bulk materials because of their high ratio of surface area to volume. FeCo alloy nano-particles with soft magnetic properties are demanded for various applications such as optics, eletronics and magnetics. Through the polyol method, highly purified particles with mono-dispersibility in various sizes can be produced and used as high-tech functional materials. In this study, the magnetic characteristics of FeCo alloy with Ag seed added in the production process of mono-dispersed nano-particles through the polyol method were investigated. Nano-particles have several interesting properties which are not shown in bulk materials because of their high ratio of surface area to volume. FeCo nano-particles with soft magnetic properties are demanded for various applications such as optics, eletronics and magnetics. Through the polyol method, highly purified particles with mono-dispersibility in various sizes can be produced and used as high-tech functional materials. In this study, the magnetic characteristics of FeCo alloy with Ag seed added in the production process of mono-dispersed nano-particles through the polyol method were investigated.