The Indian ace needed just 42 minutes to quell the challenge of the world No 10, winning 21-16, 21-13.
The top seed will take on 2011 World champion and 2012 London Olympics silver medallist Wang Yihan, who has beaten her nine times.
However, Saina can take heart from the fact that she defeated the Chinese twice this year, at the All England Championships and World Championships.
Coming into the match with a 3-0 record, Saina engaged the Japanese in long rallies before scoring winners.
It was Okuhara who surged ahead and led 5-2, but the Indian did well to draw abreast at 5 and establish an 11-8 lead at the break.
Though the Japanese kept attacking, Saina held firm despite committing some unforced errors to take the first game easily.
In the second game, Okuhara again engaged Saina in rallies but did not have enough power in her strokes to trouble the Indian. She won a point here and there by tossing the shuttle to the rear, but Saina was always a step ahead and led 11-3 when Okuhara hit a couple of shots wide.
After the break, though Okuhara gathered a few points when Saina hit wide and made some wrong line judgement calls, there was nothing she could do to prevent the Indian from winning.
Image: Saina Nehwal
Photograph: MANAN VATSYAYANA/AFP/Getty Images