The navy court held Suchkov solely responsible for the accident, rather than any of the other officers in the chain of command between him and the submarine commander.
Suchkov, who was suspended of his duties last fall, has maintained his innocence, and supporters say he was made a scapegoat in a show trial.
Suchkov's lawyers said Tuesday they would appeal.
"We believed that the investigation would be objective and [investigators] would thoroughly look into the details of the case. Unfortunately, this did not happen," Suchkov told reporters after the trial, Interfax reported.
Suchkov said he was not trying to duck responsibility for the accident, but did not consider the criminal prosecution against him fair.
The K-159 nuclear submarine sank in the Barents Sea while being towed to a scrap yard.
Nine of the 10 crew members on the K-159 drowned when a fierce storm ripped away pontoons supporting the submarine.
The sinking occurred on Aug. 30, near the site where the Kursk submarine sank in August 2000, killing all 118 sailors on board.
Suchkov also said he had come under pressure during the investigation, but did not elaborate. His trial started Jan. 12.
Prosecutor Igor Murashov said Tuesday that he was satisfied with the verdict, because it was based on "a thorough analysis and unbiased evaluation of the evidence."
Murashov earlier had asked the court to sentence Suchkov to a four-year term to be served in a special village for prisoners.
In March, the commander of the Navy, Admiral Vladimir Kuroyedov, took the stand to testify against Suchkov.
Navy spokesman Igor Dygalo said the sinking and the trial "reflected on the reputation" of the fleet, but that prosecutors had apportioned blame for the accident correctly.
"Of course, all this is said, but the men died and this is a fact to be dealt with," Dygalo said.
But many of Suchkov's supporters disagreed that he was the only official responsible for the disaster.
Igor Kurdin, head of the St. Petersburg-based veteran seamen's club, said that there were a number of Navy officers and technical personnel who were involved in planning and conducting the towing operation.
"This is a political trial aimed at holding a public whipping," Kurdin said by telephone from Odessa.
Kurdin said that he, along with 29 acting and retired admirals, had signed an open letter in Suchkov's defense.
He also noted that no Navy official had been convicted in the sinking of the Kursk.
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