Abstract: The toxic and harmful gas is one of the main risk sources of gold mine. Through investigation，study and field measurement in a certain gold deposit，the composition of toxic and harmful gas is the oxides of C，N，S which mainly come from blasting fume and tail gas from trackless equipment. Their influence factors are different at different locations. The intercepted blasting fume releases slowly and results into high concentration of harmful gas within a short time in stope and tunneling. Due to numerous trackless equipment in transport roadway and ramps，the concentration of harmful gas is mainly affected by the quantity of trackless equipment，the total power of internal combustion engine，and ventilation volume. Among these，the concentration of CO has a great relationship with the ventilation volume.

Key words: Toxic and harmful gas, Blasting fume, Source, Composition, Disaster