China is a country with multi-religions. For the moment, there are six main religions in china including Taoism, Buddhism, Islam, Catholicism, Christianity (Protestant), and Confucianism. The organizations of each religion can establish colleges, print and issue books, initiate social charity service based on their religion needs, of course must abiding by Chinese policy and laws.
Taoism: Taoism was originated in A.D. 2 in the ancient China and has more than 1,700 years history by now. There are over 9,000 Taoist temples and 5 colleges established in China.
Buddhism: Buddhism was generated in India and was introduced into China at A.D. 1, with 2,000-year history. According to the stastics, there are over 33 thousand buddhist temples and 200 thousand monks and nuns.
Islam: Islam was introduced into Sinkiang of China in the Northern Song Dynasty by Arabia merchants. In the 16th century, almost all people in Sinkiang believe in Islam. In the modern China, Islam becomes the main religious belief of Hui group, Uygur ethnic group and other eight minorities.
Catholicism: It was introduced into China since the seventh Century, peaking during the Opium War. There are about 15 million Catholics, 7,000 teachers and 6,000 churches and clubhouses in China.
Christianity (Protestant): It was introduced into China in the early nineteenth Century. China existing Protestant cover about 20 million people and more than 25 thousand churches.
Confucianism: Confucianism, as the most influential school of thought in the ancient China, was estabilished by Confucius during the Spring and Autumn period.
If you are still curious about what is the dominant religion in China, I have to say that all of the religions I mentioned above are popular in China. And there is no formal announcement about this question. But according to observation, most of my relatives of mine especially the elders believe in Buddhism.