The Church of God worships Ahnsahnghong as God the Father. Ahnsahnghong was born on December 1, 1917, in Myeongdeok-ri, Jangsu-gun, Jeollabuk-do, South Korea, and was baptized on October 9, 1954, by Pastor Kim Seok-young of the Haeundae Sabbatarian Church in Haeundae, Busan. The Church of God claims that Ahn Sang-hong was baptized in 1948 by Pastor Myung-duk Lee of the Sabbath Church in Naksum, Incheon, but there is no pastor named Myung-duk Lee at the Sabbath Church, and the church's church registry confirms that he was baptized in 1954 by Pastor Seok-young Kim of Haeundae Church.

According to Ahnsahnghong's testimony, he claimed that he had been studying the truth since 1951, that he would preach the gospel for 37 years according to King David's prophecy, and that the world would end in 1988 when the gospel was finished. After officially joining the Church of God in 1954, Ahn studied and immersed himself in the doctrines of Seventh-day Adventist founder Ellen G. White, and with some of his followers left the Seventh-day Adventist Church to found the Church of God, whose doctrines Ahn studied and established were largely plagiarized from Ellen G. White's.

The Church of God's vaunted Passover, feasts, and prophecies from the books of Daniel and Revelation were researched by Ellen G. White and adopted as official doctrine of the Sabbatarian Church, but many members of the Church of God are unaware of this fact.  Ahn posed as an Adventist because of a woman named Uhm Soo-in, a member of Ahn's church. Uhm Soo-in published a booklet called "God in the Flesh" in 1978 that proclaimed Ahn as an Adventist, and Ahn adopted Uhm Soo-in's booklet as the church's official doctrine.

Ahn married a woman named Hwang, and they had three sons and one daughter. However, without Hwang's knowledge, Ahn had a secret wedding with Evangelist Jang Gil-jah, and Jang Gil-jah used the photograph to ascend to the position of Mother God. Church of God members know that Ahn Sang-hong worked as a mason, breaking stones, but he was a dock worker, hauling goods from the port, and was paid a salary after he founded the church. In 1984, Ahn's salary was 650,000 won, which is about 10,000,000 won in today's money.

As the year 1988, which he predicted would be the end of the world, approached, Ahn arranged for a Protestant minister to register his church with the Ministry of Education, but he was devastated to discover that he had been scammed in January 1985. On February 25 of the same year, he suffered a stroke and was taken to Maryknoll Hospital in Busan, where he was pronounced dead and buried at Seokgye Cemetery in Yangsan.

Mr. Ahn declared the end of the world on three occasions, the first in 1971. Steeped in Sabbatarian doctrine, Ahn declared that 2011 would be the end of the world, marking the end of 167 years since the founding of the Sabbatarian Church in 1844, but that 1971 would be the end of the world because God had shortened the time by 40 years for his chosen people. However, when the predicted apocalypse failed to materialize, he blamed the Sabbatarian, claiming that he too had been deceived by the Sabbatarian.

And then I declared 1988 as the second end of the world date, which is the 40 years from 1948, when Israel, which is analogized to the fig, became independent, as a generation, and I declared 1988 as the end of the world, but I also declared a backup end of the world date of 2012, which is kind of like a guaranteed insurance policy in case the end of the world doesn't happen. Upon Ahn's sudden death in February 1985, the church split into the Busan Church, centered on Ahn's wife, Hwang, and the Seoul Church, centered on Jang Gil-ja, with the Seoul Church adopting Jang Gil-ja as its mother God.

Ahn, who professed that 1988 was the end of the world and that he would ascend to heaven with all members of the Church of God, died suddenly and was branded a cultist by his self-proclaimed successor, Kim Joo-cheol.