A manufacturing method for a packaging structure of SIP (system in package) includes the following steps. First step is providing a substrate having electronic devices thereon. Second step is covering the electronic devices by a mixture of a molding compound and a conductive polymer precursor so as to form a molding structure, wherein the substrate, the electronic devices and the molding structure forms a collective electronic module. Third step is separating the collective electronic module into a plurality of individual electronic modules. Fourth step is performing a doping step by using a doping element for transforming the conductive polymer precursor in the mixture into a conductive layer near the surface of the molding structure. Therefore, the manufacturing method is optimized for forming a shielding structure of the SIP module.