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In this letter, the limited feedback scheme in MIMO-Relay systems is considered. We propose a new strategy that optimizes the allocation of feedback bits between channel direction information (CDI) and phase information (PI) for multi-relay systems under the total number of feedback bits constraint. The proposed scheme eventually trades off some CDI bits for PI feedback to diminish the phase ambiguity. Simulation results show that compared to the conventional and the 1-bit PI feedback methods, the proposed scheme remarkably improves the system performance without increasing the feedback overhead.