Wang Yi, pastor of the Early Rain Church in Chengdu, Sichuan province, was imprisoned on charges of "inciting to subvert state power" and "illegal business operations".
His church said on Facebook that the pastor had been jailed for "proclaiming the gospel".
In addition to the prison sentence, the pastor has lost his political rights for three yeas and been fined 50,000 RMB (around $7,100 or £5,500).
CSW chief executive Mervyn Thomas said the charges were "baseless".
Pastor Wang's imprisonment is the latest stage in an ongoing struggle between the Chinese authorities and the Early Rain Church after he and over 100 other members of the congregation were detained on 9 December 2018.
Among those detained was his wife Jiang Rong, who was later released on bail.
The crackdown on the church came after Pastor Wang publicly criticised the government's treatment of unregistered churches and new religious regulations introduced by China last year tightening the state's control of church activities.
Earlier last year, the pastor was detained overnight and accused of "picking quarrels and causing trouble" after the authorities detained or removed over 200 members of Early Rain Church to stop them from holding a prayer vigil for victims of the Wenchuan earthquake of 2008.
In August this year, the UK Working Group on Arbitrary Detention said that the detention of the pastor and his wife had been arbitrary.
Mr Thomas called for the immediate release of Pastor Wang and other detained Early Rain church members.
"CSW condemns the sentencing of Pastor Wang Yi, who has been convicted on baseless criminal charges simply for standing up for his beliefs," he said.
"We call on the Chinese authorities to drop the charges against Pastor Wang and to release him and all remaining members of Early Rain Church from detention."