On June 5, 1972, the United Nations held its first conference on the Human Environment in Stockholm, Sweden, and adopted the Declaration on the Human Environment and the "Action Plan" for the protection of the global environment. All delegates suggested that the opening day of the Conference be designated as "World Environment Day". In October of the same year, the 27th session of the United Nations General Assembly, based on the recommendations of the Stockholm Conference, decided to establish the United Nations Environment Programme and officially designated June 5 as "World Environment Day". Every year since 1974, the United Nations Environment Programme has established a theme for World Environment Day and carried out related publicity activities.

"World Environment Day" is established to remind the world to pay attention to the changes in the global environmental condition and the harm caused by human activities to the ecology, call on people around the world to protect the environment on which human survival depends, consciously take actions to participate in environmental protection, and ask governments and the United Nations system to contribute to the promotion of protection. Each year on June 5, the United Nations Environment Programme will choose one of its member countries to hold the "World Environment Day" celebration, publish the "Annual report on the state of the Environment" and recognize the "Global 500 best." On the occasion of the 50th anniversary of the First United Nations Conference on the Human Environment, China has chosen "Building a Clean and Beautiful World" as the theme of the Environment Day, aiming to encourage the whole society to enhance awareness of ecological and environmental protection and participate in the construction of ecological civilization. While building a beautiful China, China will further reflect its role as an important participant, contributor and leader in the construction of global ecological civilization.