Abstract: To better adapt the content-centric feature of next-generation communication networks, it's necessary to consider caching function for RRHs in Cloud-RAN. This paper intends to design the optimization algorithms and reduce the system transmission delay by designing suitable caching schemes. Based on the hybrid automatic repeat request (HARQ) retransmission mechanism, the orthogonality between the fronthaul link and the download link spectrum channel, the system employs the Markov chain theory to establish the minimization optimization problem of system transmission delay. Considering the optimization objective function expression could only be obtained recursively, the Brain Storm Optimization (BSO) algorithm is introduced to solve the non-convex problem and obtain the optimal caching scheme. The experimental results show that the algorithms proposed in this paper can effectively reduce the transmission delay of the system, which meets the requirements of communication system in the future.