In this paper, a synthesis of a doubly RC terminated RC polyphase filter is proposed. The terminating circuits on both sides are composed of resistors and capacitors connected in parallel. Especially, in many cases, the terminating circuit at the load side becomes an equivalent circuit of the following building blocks such as MOS amplifiers. It is described that the transfer response of the proposed circuit becomes the same as that of the conational one. The proposed circuit is obtained through the coefficient matching method in the same as the conventional polyphase filter. In addition, the RC-parallel circuit at the source side is approximately modified to the RC-series one in order to take the source resistance included in the voltage source into account. As an example, a third-order doubly RC terminated RC polyphase filter and its approximately modified one are designed. The validity of the proposed method is confirmed through computer simulation and experiment.