Abstract: In parallel to the developing economy, the increase in the energy demand has accelerated the consumption of fossil fuels and greenhouse gas emissions. Under the dual burden of energy and the environment, the world has achieved the consensus of developing renewable energy resources. These resources have advantages such as sustainability and environmental friendliness, yet they are unavoidably unstable, unpredictable and discontinuous. To resolve these disadvantages, hybrid renewable energy systems（HRESs） integrating more than one type of renewable energy is drawing more attention and application. These systems usually include multiple objectives such as minimizing costs, maximizing reliability or reducing greenhouse gas emissions in the process of planning and designing. Therefore, it is necessary to study the optimization methods for HRES to balance different objectives, thus making various types of energy better complementary. This article reviewed the optimization techniques developed until now to solve this problem, especially the application of multi-objective optimization methods, and points out the direction of future research.