Georgia Varley died when she fell between the carriage and platform at James Street station in October 2011.
Christopher McGee, 45, had denied manslaughter but was found guilty at Liverpool Crown Court on Wednesday.
Sentencing him, Mr Justice Holroyde said McGee had taken a "terrible risk" with Georgia's safety.
McGee signalled for the driver to depart as Georgia, who was drunk, stood on the platform leaning against the train.
During the two-week trial, the prosecution said McGee should have been able to see she was in an "intoxicated state".
He told the jury he did not know how drunk she had been and thought she was moving away from the train when he gave the signal to depart.
Georgia Varley, 16, had been at a house party before she went into Liverpool for a night out
The jury unanimously found McGee, of Wallasey, Wirral, guilty of manslaughter by gross negligence.
Mr Justice Holroyde told him: "Georgia's life was ended in a dreadful way at the age of just 16 by your gross negligence.
"You did not intend to kill or even injure her, but you displayed an appalling disregard for her safety, and she paid for your criminal negligence with her life."
The judge added McGee, who had worked as a guard for Merseyrail since 1992, had "years of service and training", which was an aggravating feature of the crime.
"You must have known that a passenger who falls between the train and the platform is likely to be killed," he said.'Duty of care'
"As the guard of the train, you were in complete control of the movement of the train.
Christopher McGee was jailed for five years at Liverpool Crown Court
"Much has been made on your behalf during this trial of how intoxicated Georgia was but that did not relieve you of the duty of care which you owed to her.
"Your decision and your action determined whether Georgia Varley was safe from risk."
Georgia, from Moreton, Wirral, had been at a house party on 22 October 2011 before she went into Liverpool for a night out with friends.
CCTV shown to the jury showed her mistakenly getting off the train just before 23:30 BST, before turning around and leaning against the side as she realised her friends were still on board.
The Birkenhead Sixth Form College student was then seen to stagger and fall down the gap as the train moved off, before stopping after travelling about 30ft (9m).
A blood analysis following her death showed she had 236mg of alcohol per 100ml of blood in her system - the legal driving limit is 80mg.
She also had the drug mephedrone, also known as M-cat, in her system at the time of her death.
Georgia Varley's mother Paula Redmond said her family "had been destroyed"
Completing his sentencing remarks, Mr Justice Holroyde told McGee: "In my judgment, the CCTV footage is unequivocal, Georgia Varley was not moving away and she was not showing any sign of moving away.
"She only moved when the movement of the train deprived her of support and caused her to lose balance and fall to her death.
"I am satisfied that you merely hoped and assumed she would get out of the way when the train began to move, and on that wholly inadequate basis you took a terrible risk."
Speaking after Wednesday's verdict, Georgia's mother Paula Redmond, 41, described her daughter as "wonderful".
"We have listened as our daughter was portrayed as being a drunken liability when, in all honesty, she did no more than what many teenagers do of a weekend - she went out to celebrate her friend's birthday.
"The only liability that night was a train guard whom Georgia had the catastrophic misfortune to encounter, for he had very little, if any, regard at all for our daughter and her safety."
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Edited by devil, 19 November 2012 - 08:26 PM.