A study was conducted for the effects of input energy on fume formation ratios based on electrode(FFR$_{electrode}(g/kg_{electrode})),;deposited;metal(FFR_{weld}(g/kg_{weld}));and;slag(FFR_{slag}(g/kg_{slag}));at;CO_2$ flux cored arc welding on stainless steel. Experiments were run in well designed welding fume box. Six types of flux cored wires were used and three levels of current and voltages were given. The measured values of $FFR_{electrode},;FFR_{weld},;FFR_{slag};are;7.90{pm}1.47;g/kg_{electrode},;9.18{pm}1.65;g/kg_{electrode},;71.8{pm}24.2;g/kg_{slag}$ respectively. Fume formation ratios are not increased dramatically by input energy because of simultaneous increasing of melted electrodes, deposited metal and slag. The results indicate that the test of fume formation ratios in the research on production of low fume welding wire can be run at the fixed condition of input energy rather than various condition.