With the rising concern of global recognition and consensus of carbon neutrality under the circumstance of global warming and the shortage of both water resource and energy, the wastewater treatment processes should also be conformed to the energy conservation and carbon reduction. This study systematically reviewed and investigated the significance and superiorities of the current and future state-of-the-art anaerobic biotechnologies for the potential in carbon-neutral treatment processes of wastewater. Since the current wastewater treatment processes are energy-intensive and with high carbon emission, a carbon-neutral biotechnology should be capable of realizing the feasibility in the recovery of bioenergy and bioresource, and the reduction of CO2 emission during the treatment process. State-of-the-art anaerobic biotechnologies which are conformed with the carbon neutrality are specifically introduced and recommended for the effective and sustainable treatment of highstrength and low-strength wastewater. Difficulties and obstacles of anaerobic biotechnologies and corresponding enhancement strategies were also discussed in order to improve the treatment performance and the production of bioenergy and bioresource from organic and inorganic pollutants contained in wastewater, and also to achieve a net-zero carbon emission. This study suggests feasible insights into the future directions of biological wastewater treatment including anaerobic digestion, autotrophic denitrification and anaerobic ammonium oxidation, also provides a new outlook towards the development of anaerobic biotechnologies for sustainable and low-carbon wastewater treatment. This study also helps to popularize the concept of carbon neutrality in the research area of wastewater treatment with energy conservation and emission reduction.