Nano-size Bi-YIG (Bi substituted Yttrium Iron Garnet: Bi1.8Y1.2Fe5O12) particles and their coated film were prepared. The particles were made by coprecipitation and heat treatment processes. The magnetic ink and coated films were prepared with milling and printing techniques. We optimized the ink preparation and coating conditions. The particles in the films were observed by a transmission electron microscope and an atomic force microscope. The size of the coprecipitated particles was about 10-20 nm, The milled particles size was the same as the coprecipitated particle. The magnetic and magneto-optical properties of the particles and coated films were investigated. The maximum value of the figure of merit was 1.5 degrees which was comparable to the value of a sputtered film. The magneto-optical ink and coated film are new materials for magneto-optical devices.