The pigsty was located at the Shandong province, where buyers typically paid up to 100,000 yuan ($15,000 USD) for each "bride", aged between 20 and 30, police said.
The women were bought from their families in southern China for 3,000 yuan to 5,000 yuan ($500 — $800 USD) on promises that they would be married to well-to-do suitors, the South China Morning Herald newspaper reported.
"Once you mention a girl would be married into a good family, their parents don't ask too many questions," the newspaper quoted one of the detainees as saying.
He added that mentally disabled girls were considered a burden by their families, who did not even try to get in touch with their dear ones after they were sold.
The buyers were mainly older poor men who could not afford a conventional marriage, a police spokesman said.
The gang is believed to have collected more than 600,000 yuan ($10,000 USD) in two years from trafficking the women.
Due to the country's one-child policy, Chinese families in rural areas traditionally favor sons, something that Chinese health authorities said led to a serious gender imbalance. According to official statistics, about 118 boys are born for every 100 girls in China, as compared to a global average of 103 to 107.