Chaoyang District Court rejected Ai's appeal of a ruling handed down by Beijing tax authorities last year. Ai, who argued the tax authorities failed to follow procedures, was prevented by police from attending the hearing, The New York Times reported.
He told reporters he would file lawsuits in other courts.
"If we don't keep suing them, we've lost our basic responsibility as citizens," he was quoted as saying.
Ai, 55, was detained in April 2011 at Beijing International Airport as he prepared to board a flight to Hong Kong. Ai said he was taken to a secret detention center where he spent 81 days in confinement.
The Chinese government accused Ai's design company of evading $2.4 million in taxes. The terms of Ai's bail prevented him from leaving Beijing for a year and he was told not to use social media or talk to reporters.
Ai gained international prominence as an artist for his involvement in the design of Beijing's "Bird's Nest" Olympic stadium. He fell out of favor with the government, however, after his criticism of the Olympics and the May 2008 Sichuan earthquake, the BBC said.