Feng became the first player on the LPGA Tour to defend a title this season with a total of 19-under par 197 at the Taiheyo Club's Minori Course in Ibaraki.
"That was my goal, before I started the week, to defend my title," said Feng.
"My caddie told me: 'This week, you're going to be first. Two weeks ago, you finished third. Last week, you finished second, so you know what comes after that'."
Feng held a two-shot lead over Japan's Suzuki going into the final round but had a rollercoaster start, with two bogeys and two birdies in the first four holes.
The Chinese Olympic bronze medallist tucked away her first par at the fifth and from then on played blemish-free golf.
Feng's sixth birdie of the round at the 17th proved enough to hold off the charging Suzuki, who fought all the way but blew her final chance with a bogey at the 18th when a birdie would have forced a playoff.
"(Suzuki's) ball striking is so good. She left herself so many birdie chances and I was freaked out," Feng admitted.
"Before I started the round, I told myself to not look at the other scores."
It was Feng's second win of the season after the Volvik Championship in Michigan in May and her eighth LPGA win overall.
Helped by a stunning hole-in-one on the third, Sweden's Anna Nordqvist shot a six-under final round of 66 to finish third on 15-under par, two behind Suzuki.