South Africa's forwards laid the platform for the nine-try win, dominating at scrum time and repeatedly powering over the gain line with pick-and-drives and mauls.
The Bok Women made the most of the wet and blustery conditions, with their set-piece work proving particularly effective. They led 27-7 at half-time after tries from props Xoliswa Khuzwayo and Nombuyekezo Mdliki, Lindelwa Gwala, Vainah Ubisi and Sizo Solontsi.
Khuzwayo's opener came after a clever training-ground move from a lineout, while Gwala and Solontsi both crossed from powerful driving mauls.
Fiji briefly threatened a comeback after Adi Vani Buleki scored early in the second half to make it 27-12, but their hopes were quickly dashed when No 8 Alfreda Fisher's yellow card for a high tackle on Catha Jacobs was upgraded to a red.
Khuzwayo added her second try soon afterwards before Maceala Samboya finished a slick backline move to put the result beyond doubt.
Fullback Byrhandre Dolf then crossed after another well-worked set piece before replacement flanker Sinelitha Noxeke rounded off the scoring with her first Test try.
Dolf finished with 13 points, while South Africa's defence also stood firm against Fiji's dangerous counter-attacking game, limiting the hosts to two tries.
The Springbok Women will now look to complete a series sweep when the sides meet again next week.
Assistant coach Laurian Johannes-Haupt and debut captain Libbie Janse van Rensburg praised their team’s performance in the Springbok Women's dominant 55-12 victory over Fijiana XV.
Springbok Women assistant coach Franzel September is confident everyone in the squad is aligned to deliver their best effort for team and country against Fiji on Saturday.
Flyhalf Libbie Janse van Rensburg will become the 12th captain of the Springbok Women when she leads them out against the Fijiana XV in Suva on Saturday.
The latest Springbok Women's training squad included no fewer than nine uncapped players ready to assemble for two camps.
