In August 1925, 54 countries, including China, held the "International Conference on Children's Happiness" in Geneva, Switzerland, and adopted the "Geneva Declaration on the Protection of Children", calling on all countries in the world to establish "Children's Day".

On March 7, 1931, the Chinese Salesian Association submitted a proposal to the Shanghai Municipal Social Bureau and forwarded it to the Nanjing government authorities, suggesting that April 4 be designated as Children's Day. On August 17, the Ministry of Education of the Nanjing government approved the proposal, and decided to officially designate April 4 as Children's Day from the following year (1932). The next day, major newspapers and periodicals such as Shanghai's "Declaration" and Peiping's "World Daily" immediately published this official notice, and the general public gradually became aware of the "April Fourth Children's Day".

As stated in the proposal of the China Salesian Association, the establishment of Children's Day aims to "attract the attention of the people, so that everyone can have the idea of Salesians, everyone will be responsible for Salesians, and children will be able to know their own status, expand the scope of Salesians, and build the foundation for strengthening the country and seeds". This original intention has won the unanimous recognition and support of people from all walks of life, including Cai Yuanpei, Song Qingling, Huang Yanpei, Tao Xingzhi and so on, and the "April Fourth Children's Day" has also taken root in China.

As for why Children's Day was chosen on April 4, there was no official unified explanation at that time, but three years later (1934), when Cai Yuanpei attended the fourth Children's Day commemorative meeting in Shanghai, he improvised in his live speech and gave a reasonable and ingenious explanation.