Martinez Sanchez, seeded sixth, defeated Galina Voskoboeva 7-6 (7--0), 7-6 (7-2) in a match that took more than two hours. It was the fifth WTA title for Martinez Sanchez and second this year. She won at Bad Gastein, Austria, in July.
Martinez Sanchez, whose four previous tournament championships all came on clay courts, didn't drop a set en route to the Korea Open title.
She swept through the first tiebreaker and fought off three set points for Goskoboeva before forcing the second tiebreaker.
"I felt very calm in the tiebreaks. That was the key for me," Martinez Sanchez said. "I felt I played well the whole match. I like coming to net and I think it also makes my opponents uncomfortable, so it works well.
"But Galina played well -- this was my toughest match of the week. I had to fight until the end."
Martinez Sanchez collected $37,000 for the tournament win while Voskoboeva, who was appearing in her first WTA championship match, earned $19.000.