The youth internationals scored five in the first half and four in the second to record their biggest win for over 40 years, with Raheem Sterling among the many to hit the net
First-half goals from Michael Keane, Raheem Sterling, Danny Ings, James Ward-Prowse and Thomas Ince gave the hosts an emphatic lead going into half-time having controlled the first-half with ease.
The action resumed in similar vein in the second half as Ings bundled the ball over for the sixth before Sterling added his second and Carl Jenkinson and Will Hughes completed the rout.
England were missing top goalscorer Saido Berahino via suspension, thus allowing Burnley striker Ings the chance to impress up front as one of five changes, while Wilfried Zaha sat on the bench.
Meanwhile, the visitors made three changes from their 2-0 defeat against Moldova on Friday with Mirco Ciambotta, Lorenzo Liverani and Marco Bernardi all starting for the bottom-placed side.
The Young Lions took five minutes to open the scoring last time these two sides met in a 4-0 victory as Keane opened the scoring and Harry Kane hit a hat-trick and it proved a similar story.
It was Keane again who gave England the lead on this occasion, just after 10 minutes, as he rose high from an Ince corner to head a looping ball over the defence and into the corner of the net.
Shortly afterwards, England had doubled their lead through Sterling, who – inside the box – had his shot on goal blocked although San Marino's desperate attempts to clear failed as it rolled in.
Ings, who was making his second appearance for the Under-21s, then gave his side a quick third after finding space in the box to meet a right-wing cross with a cushioned header off the post.
Ward-Prowse then added a fourth goal with a stunning free kick that was weighted perfectly away from the keepers reach before Ince netted one of his own after Ings pulled the ball across the box.
Ince, who had earlier provided the assist for the opening goal, had now scored the final goal in a comfortable first-half display for England where his trickery was a constant threat on the right.
The second half started in similar fashion with England finding an early goal. An attack from the left saw the ball enter the box and Ings dispatched with a scrappy goal similar to the second.
Sterling had his second ten minutes later, lifting the ball into the net over an onrushing keeper. Jenkinson got in on the act almost immediately afterwards with a well-struck shot across goal.
England were in cruise control at this stage and had eclipsed their record win of 8-1 against Finland back in 1977. Hughes then edged them closer to double figures with a stunning strike from distance.
But the Young Lions ended the game with nine as they now take a six-point lead at the top of Group 1 with three games to play and a crunch match with Wales in March next up on the list.