Forward Georgia Stanway broke the deadlock from the spot in the 40th minute, sending a powerful strike past South Koreald keeper Kim Jung-Mi after Lauren James had been brought down in the area.
Winger Chloe Kelly doubled their advantage 16 seconds into the second half after her shot from the edge of the box took a deflection to loop over Kim and into the net.
Four minutes later Alex Greenwood set up Alessia Russo inside the six-yard box and the forward made it 3-0 with a chipped finish, while James added one more, her first for her country, to complete the rout 12 minutes from time.
England's players wore black armbands in tribute to the victims of the earthquake in Turkey and Syria, and in memory of injured forward Beth Mead's mother, who died last month.
European champions England are next in action on Sunday when they take on Italy who lost 2-1 to Belgium earlier on Thursday. The Lionesses will face Belgium in their final match on Wednesday.