Authorities took Pastor Bao Guohua, his wife and five church employees into custody at Holy Love Christian Church in Jinhua, in eastern Zhejiang province, accused of embezzlement and disrupting social order.
But, the church's lawyer Chen Jiangang told the BBC it was actually a row over church crosses.
The Chinese government has been destroying and tearing down church crosses across the country in what is said to be a bid to stamp out unauthorised religion.
Only a few churches in China are state sanctioned and those that are not often face persecution.
The church had refused orders to remove the cross from its building, the lawyer told the BBC.
He added: "I can tell you that if church leaders had agreed to take down the cross, there would have been no problem. But they refused. That's why they were detained.
"What is unusual is that this was an official church, recognised by the Communist Party. Everything had been properly approved by the authorities."
State media said the group had embezzled large sums of money and "conducted illegal business".
They were "deliberately hiding accounts, and on several occasions distorting the truth to incite social unrest among believers," state media accused.
Tanya Corbett from anti persecution charity Open Doors told Premier it was concerning.
"That does indicate a worrying trend," she said, "it's interesting that there about 85 million Christians in China."
She added that many of them face "watching and perhaps a more passive form of persecution" where pastors are questioned by police often.