BEIJING, October 5, 2014 (AFP) - The 23-year-old, who shot a total of 69 Sunday and 277 during the tournament, had been joint overnight leader with Swede Caroline Hedwall before finishing with a birdie on the 18th hole.
Hedwall shot an even par 73 on Sunday to finish on a 13 under par total of 279 for second place.
Number one ranked player Stacy Lewis, who had led or tied for the top spot during the first three rounds, ended the day on 75 and a tournament total of 11-under par, to tie for sixth.
The Pine Valley Golf Club win was Lee's second in less than three months after the 2014 Meijer LPGA Classic.
"I really didn't think I would get my second win this quickly." said Lee, who finished 15 under par.
"I was a lot more nervous this time than first time around. I think I made a few mistakes towards the end, especially on the 18th. I'm really happy I won the tournament, and it was good."
In joint third place were Koreans Haeji Kang, Inbee Park and America's Brittany Lang.
Final scores (par 73):
277 - Mirim Lee (KOR) 70-68-70-69
279 - Caroline Hedwall (SWE) 67-71-68-73
280 - Haeji Kang (KOR) 69-72-70-69, Inbee Park (KOR) 69-72-68-71, Brittany Lang (US) 70-66-72-72
281 - Mi Hyang Lee (KOR) 69-76-69-67, Stacy Lewis (USA) 66-68-72-75
282 - Pornanong Phatlum (THA) 72-75-67-68, Ilhee Lee (KOR) 69-70-71-72
283 - Chella Choi (KOR) 71-70-70-72
284 - Mariajo Uribe (COL) 73-69-72-70, Yanhong Pan (CHN)71-68-73-72, Suzann Pettersen (NOR) 74-66-70-74
285 - Yuting Shi (CHN) 74-69-68-74
287 - Pernilla Lindberg (SWE) 72-70-71-74, Kelly Tan (MAS) 74-70-69-74, Belen Mozo (ESP) 69-69-72-77, Caroline Masson (GER) 70-68-71-78
288 - Na Yeon Choi (KOR) 75-71-69-73, Sandra Gal (GER) 72-69-72-75, Jenny Shin (KOR) 68-73-72-75, Yani Tseng (KOR) 69-75-69-75, Mi Jung Hur (KOR) 73-71-67-77, So Yeon Ryu (KOR) 72-69-70-77, Sun Young Yoo (KOR) 68-73-69-78