Khan pleaded guilty last month to charges that included the beheading plot, which was foiled by police and Britain's MI5 security service a year ago.
Khan also admitted sending equipment such as night-vision cameras, balaclavas and computers to Pakistan to be used by fighters against US and British troops in Afghanistan.
The prosecution said that Khan had planned to enlist drug dealers to help kidnap a Muslim soldier on a night out in Birmingham.
The victim was to be seized, bundled into a car and taken to a lock-up garage.
"He would be murdered by having his head cut off like a pig," Rumfitt said. Prosecutors said the expression "like a pig" was Khan's own.
Film of the killing would then be released to the media.
Several other men were also on trial with Khan.
Basiru Gassama, 30, was jailed for two years for failing to disclose information about the plot.
Mohammed Irfan, 32, Zahoor Iqbal, 30, and Hamid Elasmar, 44, all from Birmingham, were jailed for between three and seven years for related charges under the UK's "anti-terrorism" laws.
General Sir Richard Dannatt, the head of the British army, said he welcomed the conviction "of a group of men who were prepared to conduct such a cowardly and grotesque attack against members of the army based solely on their religion".
Amjad Mahmood, 32, was cleared of helping to supply equipment and failing to disclose information about the kidnap plot.