Yan and Buhai share lead at LA Championship
But on a day of low scoring at El Caballero Country Club, Sweden's Frida Kinhult was just a shot off the leading pair and a chasing pack of five were just a further stroke behind.
Liu made a shaky start with a bogey on her opening hold, the par-4 10th, but she was electric from then on making birdies on three of her next four holes before an eagle on the par-5 16th.
She finished her round with three birdies in a row and carded her lowest score on the LPGA Tour.
"I think on my first hole I was a little nervous.