Energy extraction and conversion from ocean waves are being increasingly regarded as a research hotspot. Many different wave energy conversion systems have been proposed to convert wave energy into electricity. The paper reviewed and analyzed the hydraulic transmission technologies used in various kinds of wave energy conversion systems, and introduced a water/oil integrated transmission system used in wave energy converter to reduce the pollution caused by hydraulic oil leakage. This paper also proposed a digital hydraulic cylinder group, which could regulate the pressure of hydraulic power take-off system and reduce the energy interference in multiple devices deployed in arrays. The wave power generation applications will develop rapidly due to the fading fossil energy resources and serious environmental pollution, while the hydraulic transmission technologies with water/oil integrated transmission and digital hydraulic cylinder group will be of crucial importance to the process of the development.