Ozawa was unopposed in DJP presidential race, Kyodo news service reported.
Elections to lower house of parliament are likely soon in the wake of the recent resignation of Japanese Prime Minister Yasuo Fukuda.
Ozawa, 66, could become Japan's next prime minister if he can guide his party to a victory in the polls as he did to his help his party win control of the upper house last year, Kyodo said.
"The DPJ will create a new administration that will revive Japan, by toppling the (coalition) government of the Liberal Democratic Party (of Fukuda) and the New Komeito which takes no notice of the public's lives," Ozawa was quoted as saying as part of his basic policy plan.
Fukuda's LDP will have its presidential election this month with several candidates expected to run.
The report said the LDP and its coalition partner may choose to have early election if the new LDP leader wins public approval.