This invention relates to a catalyst composition for a producing process of an unsaturated carboxylic acid salt and its derivatives from carbon dioxide and olefin, wherein the catalyst composition in the present invention has been proved to be effective in catalyzing the carboxylation of carbon dioxide and olefin, wherein said catalyst composition comprises: a) a palladium metal complex as shown in structure (I); wherein, R1, R2, R3, and R4 independently represents a group selected from hydrogen atom, halogen atom, alkyl group, alkyl halide group, alkoxy group, amine group, optionally from alkenyl group, alkynyl group, phenyl group, benzyl group, or cylic hydrocarbon group comprising hetero atom; R5 represents group selected from alkyl group or phenyl group; b) a ligand selected from organophosphorus compound; c) a base selected from sodium tert-butoxide, sodium isopropoxide, sodium 2,6-dimethylphenolate, sodium 2,6-difluorophenolate, sodium 2-methylphenolate, or sodium 2-fluorophenol); and d) a reducing agent.