Ms Gillard said the trip "reflects the importance" of Australia's "evolving relationship" with the country.
She is scheduled to meet newly-installed Chinese President Xi Jinping and Premier Li Keqiang and will visit Shanghai, Beijing and Hainan island.
This is Australia's most high-level delegation to China, officials say.
"The timing of this visit so soon after the new leadership has entered into office is deliberate and reflects the importance of our rapidly evolving relationship with China and our high-level political oversight of that relationship," Ms Gillard said on Thursday, ahead of her trip.
Ms Gillard is expected to discuss energy-related matters with Chinese leaders, among other trade issues.
Talks between both countries are also expected to touch on education and regional security.
Ms Gillard's delegation includes Foreign Affairs Minister Bob Carr and Financial Services Minister Bill Shorten, among other senior Australian officials.
This is her second visit to the country in two years.
Australian Prime Minister Julia Gillard has left for China on a five-day visit aimed at strengthening ties with the country's largest trade partner.