A straight-sets win for the US looked a distant prospect in the opening set as the Chinese opened up a 13-8 lead on the back of a strong defensive showing, but a 6-1 run brought the USA back level, after which there was only going to be one winner.
The second set was similarly close, but when May-Treanor's wonderful back-court dig was touched over by Walsh for a point the US had no right to win, the Chinese pair's focus dropped and the USA pulled away.
'To come back from the deficit that we had in set one is great - they were playing awesome but we made it happen. I'm speechless. I think we played as a unit, so I'm very happy,' said May-Treanor.
'I had a picture in my head at the beginning of the season of how I wanted us to play and we're living that picture, but it's not over yet.'
Walsh added: 'I'm feeling so much relief, overwhelming joy and a lot of humility. I'm so proud of us - we didn't play perfectly, but our hearts and minds were perfect.'