In this paper, an improved relay selection scheme is proposed for multi-relay cooperative transmission network. For the proposed scheme, based on the decoding results, the relays that decode correctly will be included in the Decode-Forward (DF) group. The rest of relays will be included in the Amplify-Forward (AF) group. The relay which maximizes the minimum of the Signal-to-Noise Ratios (SNRs) of the source-to-relay and relay-to-destination channels is selected for the AF relay group. While the relay which has the maximum relay-to-destination SNR will be selected for the DF group. Then, between the selected relays from AF and DF groups, the one which maximizes the output SNR of the system will be selected as the final relay.