The invention discloses a steel-plastic composite support assembly for an automobile instrument panel (IP) and an automobile. The steel-plastic composite support assembly comprises a cross beam made of steel, wherein vehicle body mounting supports are respectively arranged at two ends of the cross beam. The steel-plastic composite support assembly also at least comprises a connection support for connecting the support assembly with a floor, an IP support for mounting the automobile IP, an air conditioner support for mounting an air conditioner, a PEPS module support for mounting a PEPS moduleand a glove box support for mounting a glove box, wherein all or part of parts of the connection support, the IP support, the air conditioner support, the PEPS module support and the glove box supportare injection molded parts made of plastic obtained by mixing nylon and glass fiber. The steel-plastic composite support assembly for the automobile IP uses the plastic injection molded parts insteadof steel parts to effectively realize the lightweight of the support assembly for the automobile IP. At the same time, by virtue of the selection of plastic material, the steel-plastic composite support assembly improves the rigidity and other performance of each injection molded part, effectively realizes the lightweight, improves the combination of modality, rigidity and strength performance ofthe entire support assembly for the automobile IP, and improves the NVH performance.