Reshetin's lawyers say the case revolves around a contract signed with a Chinese company in 1996. The contract was signed under an intergovernmental agreement between Moscow and Beijing on Russian assistance to the Chinese space sector.
Reshetin and two of his assistants, who are also in custody, are also accused of misappropriation of funds.
Reshetin's lawyers today said they are appealing his arrest, which they say was illegal.
The export company Reshetin headed was set up in 1991 to carry out contract deals in space engineering on behalf of Russia's leading Central Scientific Research Institute for Machine-building.
The FSB reportedly began its investigation two years ago.