The previous highest winning margin in the tournament was 113 runs, recorded by South Africa against Thailand in 2020.
England, who claimed the T20 World Cup in 2009, have won all four of their group-stage games and finish as Group B leaders. They will face either New Zealand or South Africa in the semis.
Nat Sciver-Brunt's unbeaten 81 off 40 balls and Danni Wyatt's 59 set up England's 213 - beating South Africa's 195 versus Thailand.
Pakistan could manage only 99-9 in response, with Katherine Sciver-Brunt and Charlie Dean picking up two wickets apiece.
Despite the heavy defeat, there was some consolation for Pakistan skipper Nida Dar, who took a wicket in the game to become the highest wicket-taker in women's T20I cricket.
"Trying to take some momentum into the semis today. The way our batters played today, it was really good," captain Heather Knight said.
