The present invention provides a preparation process of complex oxides catalyst containing Mo, Bi, Fe and Co, which comprising steps as following: dissolving precursor compounds of the components for catalyst and complexing agent in water to obtain a solution, and then drying, molding and calcining the solution to obtain catalyst. The catalyst is used for gas phase oxidation of light alkenes to unsaturated aldehydes. The catalyst has high activity, selectivity and stability. The reaction condition is mild. The preparation process of the catalyst is easy to operate and can be used for mass production.