The eighth seed was not able to deal with the consistency the world number one fought against her with and was broken for a third time as Muguruza sealed the opening set in fine style.
Latvia's top-ranked lady tennis player Alona Ostapenko defeated Puerto Rico's Monica Puig 6-2, 3-6, 6-3 to advance to the quarterfinals of the Wuhan WTA Premier series tennis tournament, reports LETA.
"I just beat number one and it's incredible", said Jelena Ostapenko. The top seed is into the quarterfinals at the tournament, facing Jelena Ostapenko next. A curling forehand crosscourt sealed her second-straight break before Ostapenko rolled through a love hold extending her lead to 3-1.
These weeks are critical for the 21-year-old as she is hoping to secure a seeded spot at the Australian Open in January.
"I didn't do much wrong in that first set, but came up short, so credit to her", Barty said.
Barty, ranked 37th in the world, failed to convert three match points in the third set but dominated the deciding tiebreak to bag her first ever win against a top-five player.
"I think she was playing just little bit better today", Pliskova said.
Up a double break, Ostapenko served for the match at 5-1 but Puig wasn't ready to go home.
She was involved in one of the best matches of the year at Wimbledon, fighting back from a set down to beat Halep to become the first British woman to reach the last four at the All England Club in 39 years.
Ekaterina Makarova of Russian Federation also made it to the quarters, beating compatriot Daria Kasatkina 6-4, 6-4.
The Latvian won a superb six in a row to wrap up the match and her first victory over Muguruza in three attempts.
"It was a pretty close match at the end", said Muguruza.
"When it gets tight or when I see myself going in the wrong way, sometimes I can go a little bit insane and lose my focus" she said earlier this week as the WTA Insider Courtney Nguyen revealed.