The latest market figure shows the total Chinese stock market worth USD 6.09 trillion, compared with USD 6.17 trillion in Japan.
The US stock market is leading in the world with the total worth of $31 trillion.
The Chinese economy suffering from the latest trade war with the US and slowing economy.
In late 2014, China overtook the second position from Japan then soared to an all-time high of more than $10 trillion in June 2015.
Chinese stock market Shanghai Stock Exchange slum 16% in this year and Industrial and tech stocks have been among the worst performers.