The development history of semiconductor gas sensors,the properties and application of doped SnO2 gas nanosensors are introduced. Effects of doping metals,metal oxides and rare-earth on the gas sensitivity of SnO2 are thoroughly analyzed. Sensitivity,stability and selectivity of gas sensor towards special gases can be greatly improved through doping. The gas-sensing mechanism of doped SnO2 nanosensors is analyzed using the oxide adsorption theory on the sensor surface. Development prospect of SnO2 gas senso...