Lena Zhu, 9, from Oatley Public School, wins junior division of Premier's Spelling Bee

Autumn brought a twinge of nerves for Lena Zhu. Silent letters had already tripped up her fellow competitors in the state final of the 2017 NSW Premier's Spelling Bee.

But Zhu, a year 4 student at Oatley Public School, said she was "pretty relaxed" through another nine rounds of the competition, correctly spelling words such as spinnaker, illustrious, mediocre and camphor.

Not even the careful enunciation of ABC newsreader Juanita Phillips could save Zhu's competitors from being stumped by words such as akimbo, mollycoddle, quantum and confiscate.

But the nine-year-old Zhu outspelled more than 40 other students to win the junior section with the word irrevocable.

Lucinda Adams, from Woollahra Public School, survived 14 rounds to win the senior section with the word charlatan.

Zhu, who aspires to be a doctor, attributed her success to a boy wizard and spelling practice with her parents.

"I read lots of Harry Potter books," she said. 

The Premier's Spelling Bee, held since 2004, is designed to improve the literacy skills of NSW primary school students.

More than 150,000 NSW school students competed in this year's competition, with 89 making it to the final held at the Eugene Goossens Hall in Ultimo on Wednesday.

The competition has two divisions: junior for years 3 and 4, and senior for years 5 and 6.

Junior spellers had to correctly spell words such as bitmap, acoustics and flannelette to compete in the state finals, while senior students were challenged with words such as pendulous, delicatessen and antiquity.

NSW Premier Gladys Berejiklian said the Spelling Bee provided an opportunity for students to learn new words and explore the English language.

"Spelling is the cornerstone of literacy, and the Spelling Bee is invaluable in promoting the development of skills necessary for clear communication," she said.

"It encourages our students to embrace a love of spelling and, in turn, a love of reading which will stay with them for the rest of their lives."