This paper theoretically analyzes the performances of opportunistic decode-and-forward relaying system with multi-relay in dependent but non-identical Nakagami-m fading channels.Based on the derived closed-form expressions for the moment-generating function of arbitrary signal-to-noise ratios,the closed-form expressions of the outage probability and the symbol error rate of the relaying system with arbitrary relays are obtained and further verified by simulation.The obtained closed-form solutions can be used to evaluate the performances of opportunistic relaying systems in Nakagami-m fading channels and provide theoretical references for practical engineering projects.