Silicon interposer based 2.5D IC can realize heterogeneous integration and is effective to implement an electro-optical system. In this paper, we analyze the CPW structure transmission line on silicon interposer for high speed electro-optical system. The RDL-TSV-RDL transmission structure is used to reduce the resonance. An optimization method is proposed to improve the performance of the RDL-TSV-RDL transmission structure by increasing the number of ground TSVs and relocating the location of these TSVs. Simulations in EM solver indicate the new design method can realize resonance suppression by slightly increasing the signal loss. The maximum insertion loss is less than 2dB. Thus, the proposed RDL-TSV-RDL transmission structure can be used to implement interconnect in high speed electro-optical system.