1. The reason why hospitals use the cross: a hundred years ago, when American missionaries evangelized in China, they saw that Chinese women died a lot due to childbirth, and especially the child mortality rate was very high, so they brought American doctors and technology to serve the Chinese, and as a result, Chinese mothers passed through the hospitals without any problems, and the survival rate of the children, in particular, was greatly improved.
The Chinese people were thus attracted to the church's sign of the cross, which guided them in the direction of medical treatment, and in the hearts of the Chinese people, the cross became a symbol of salvation, which will be commemorated forever. For this reason, when there were official hospitals run by missionaries in China, the sign of the cross was used until generation after generation habitually marked the hospitals with the sign of the cross, which was taken for granted.
2, the reason for the use of the cross in the church: the cross is now the symbol of Christianity, representing love and salvation, in 431 AD began to appear in the Christian Church, 586 AD began to be erected on the top of the church. The cross was originally used as a torture instrument to execute criminals in the Roman Empire, but after Jesus died on the cross, the cross was given a new meaning, representing God's love and salvation for the world, and is a sacrosanct and inviolable symbol.
Expanded information:
Story about the origin of the sign of the cross in Chinese hospitals:
An American Presbyterian woman missionary, Douw.D.M, who came to Peking in 1863, saw that Chinese women giving birth at home was not hygienic and had a high mortality rate. She had heard and seen all the ignorance and unhygienic practices of the old-fashioned midwives, and thought that the old method of delivering babies was almost a disaster for mothers and babies.
Superstition, in particular, victimized women and children the most, and she once saw a woman in difficult labor lose both her mother and child when the midwife put a shoe on the child's exposed foot, believing that the child would then walk out on its own. In response, Douw returned to the U.S. and prepared for 8 years to raise funds to build China's first women's hospital in Beijing in 1885, which would later become known as Daoji Hospital. As a matter of course, she hung a cross in front of the hospital.
Also in 1885, the American Christian Women's Missionary Society founded a hospital for women and children outside the west gate of Shanghai, and in 1901, the Episcopal Church in the United States founded the Guangren Hospital in Shanghai, which specialized in treating female patients. Subsequently, the Church operated hundreds of hospitals throughout China, and each hospital had a cross. after 1949, the changing times, political movements, even the Cultural Revolution catastrophe, did not remove these signs of the cross all over China's cities and towns, which can not be said to be a miracle.
Baidu Encyclopedia - The Cross
China Quanzhou Government Website - Origin of the Red Cross Movement