In this paper the coprecipitation was improved(called spraying coprecipitation)to pre-pare nano gas sensitive materials such as ZnGa 2 O 4 and ZnFe 2 O 4 .The structural analysis was done by XRD,SEM and TEM.The result shows that the size and the uniform of the material pre-pared by the spraying coprecipitation is better than ever.Transport and reaction process of spray-ing coprecipitation was analysed by hydrodynamics theory.Some experiments were explained.The principle of spraying coprecipitation was also discussed.