The national action, coordinated by union United Voice, will see workers leave work at 3.20pm on Thursday and wave placards on Commonwealth Avenue to raise awareness of their working conditions.

United Voice ACT secretary Lyndal Ryan said early childhood workers earned an average $21 an hour in a job that was "demanding and vital".

"Low wages really drive workers out of the industry," she said.

"There's a terrible turnover in Canberra ... it's an expensive place to live.

"The absolute main issue is they can't afford to do this work - we hear that from a lot of people."

Parents and children are expected to participate in Thursday afternoon's demonstration. Ms Ryan said families who may be affected by the walkout had been notified by their early childhood centres.

"We try and not inconvenience people," she said.

"Families have been notified and are supportive. Some of the services are providing some skeleton staff."

Thursday's action will mark Australia's largest early childhood education walk-off with about 10,000 families expected to be affected.

Workers will strike from 3.20pm to symbolise the time they argue they start working for free.

Canberra workers participated in a similar strike on International Women's Day in March, leaving work at 3.20pm to coordinate a 'honk-a-thon' on Commonwealth Avenue.

Ms Ryan said workers weren't properly remunerated as the industry was 97 per cent female.

"The predominance of women and the gender attitudes towards workers has helped keep wages low," she said.