Network coding may improve network efficiency. However, it is not necessary to code every link to meet a given transmission rate. In this paper, we consider the NP-hard problem of minimizing the number of coding links of a network for a given target transmission rate. Chemical Reaction Optimization (CRO) is a general purpose metaheuristic, which have been demonstrated to be effective in many optimization problems. We adopt the CRO framework to develop an algorithm to solve this NP-hard problem. Simulation results show that CRO outperforms existing algorithms with two sets of test network topologies.