Yauhen Poludzen was found guilty of abuse of office on March 25. No more details were available on the charge.
The court in Minsk also ruled that Poludzen's property will be confiscated.
He was stripped of his military rank as a colonel.
Poludzen’s relatives told RFE/RL they do not plan to appeal the sentence.
Poludzen was arrested in December 2011.
Poludzen is on a list of about 200 Belarusian individuals barred from entering the European Union.
The sanctions were put in place after Minsk's crackdown on demonstrators who protested official presidential election results that handed victory to incumbent Alyaksandr Lukashenka in December 2010.