Liquid cooling systems are mainly used for processing capability of the high thermal power density, which exceeds the physical limits of air cooling methods, to support more and more application scenarios where manufacturers are creating competitive advantages. Liquid cooling can provide heat transfer capabilities several orders of magnitude higher than that of air cooling, and applications dealing with high heat density in the core and edge computing as well as access network will increasingly require the support of liquid cooling technology. This Recommendation identifies the requirements for liquid cooling and high energy efficiency solutions for 5G BBU in Centralized-RAN mode, including requirements of immersion and spray liquid cooling technology, key indicators of immersion and spray liquid, safety requirements of immersion and spray liquid cooling system, management procedure and energy efficiency measurement method, and use cases of liquid cooling solutions. In this Recommendation a complete infrastructure solution practiced in 5G BBU is proposed that can provide safe and efficient liquid cooling technical support, which can assist in the design of full liquid cooling facilities as well as the successful introduction of liquid cooling solutions into the existing air cooling telecommunication rooms and data centres.