This paper proposes an effective method to jointly design girth-4 cycle-free Quasi-cyclic (QC) Low-density parity-check (LDPC) codes for multi-relay cooperation in a Rayleigh fading channel, where the joint iterative decoding by Min-sum algorithm (MSA) based on the introduced joint Tanner graph is also presented at the destination. Theoretical analysis and simulation show that the proposed QC-LDPC coded cooperation outperforms the randomly coded cooperation under the same conditions.