The Games are set to open on July 23 in the face of worries that an influx of tens of thousands of people from around the world could trigger another wave of infections.
China has already secured 318 spots in 224 events for 30 disciplines, the official Xinhua news agency reported.
At Rio 2016, China sent a record 416 athletes in 26 disciplines and 210 events – its biggest for an overseas Olympic Games.
China hopes to contend for gold in diving, table tennis, shooting, gymnastics and weightlifting, with medals also expected in badminton, taekwondo, sailing, rowing, karate, women’s boxing, women’s volleyball, swimming and track and field, according to Xinhua.
But China’s men’s basketball team failed to qualify for the Olympics – a first in 37 years.
Games organisers have banned spectators from overseas and set a cap on domestic spectators at 50% of capacity, up to 10,000 people.
Japan has not had the explosive COVID-19 outbreaks seen elsewhere, but has recorded over 800,000 cases and more than 14,800 deaths.
Only a quarter of its population has had at least one vaccination shot after an initially slow rollout.