The Holy Spirit Study Centre of Hong Kong's Catholic diocese says the rules, due to come in 7 October, would restrict the freedom of clergy from outside of the country and restrict the distribution of religious material on the internet.
There are concerns the rules will also restrict the recruitment of new leaders in the Church there.
Anthony Lam, executive secretary of the Holy Spirit Study Centre of Hong Kong's Catholic diocese, told the Catholic Herald: "Compared with previous drafts these regulations are more restrictive, since they include references to national security.
"They may not make a great difference for China's underground Catholic Church, since it's illegal anyway.
"But they'll have a great impact on the Church's open community, which has to report everything to the government."
Speaking last year the Chinese premier Xi Jinping said that China needed to be united against "foreign influences" in the country.
The government has also been following a policy of church cross removal, saying it is for health and safety reasons.
China ranks at number 33 on Open Doors World Watch List, which ranks persecution against Christians around the world.
There are thought to be around 14 million unofficial Catholic worshippers in China. It's thought there are 97 million Christians in total, with that number increasing
The law states that all churches are required to register and be monitored by the government, meaning many Chinese Christians worship in secret.