The Japanese sixth seed Osaka won 6-3, 6-3 in sweltering conditions at the key Wimbledon preparation tournament, with the mercury topping out at 37 degrees Celsius (98.6 Fahrenheit).
After the match, Osaka said she was thrilled to reach her first career grass court final but had her eyes on the prize.
"I'm also really happy, but there's one more match to be played, and we're going to focus on that," Osaka said.
Osaka said her daughter, who will turn three during Wimbledon next week, was already waiting in London but was not yet aware of her mother's true occupation or status in the game.
"I don't know if she knows I'm successful, I think she just knows I play tennis," said the 28-year-old.
"Sometimes when we're at home, and I pick up my tennis bag, she'll ask 'Oh, are you going to play tennis?'
"I don't know if she really likes it, but I think she knows what I do, but she probably doesn't know how good I am at it."
Osaka blasted six aces and broke her opponent once to take the first set comfortably.
Early in the second, Wang answered an Osaka break with a break of her own, but the Japanese player quickly wrestled back control of the match.
Osaka broke Wang again and took the match in one hour and 10 minutes to continue her strong grass court form just days out from Wimbledon, where she has been handed the 14th seed.
Osaka won two titles apiece on the hard courts of the Australian and US Opens, but has struggled on grass, never making it past the third round at Wimbledon.
The 28-year-old will face the winner of Friday's second semi-final between Elena-Gabriela Ruse and fourth seed Karolina Muchova.