Investors opened 362,719 accounts at brokerages on May 24, the fifth straight day the tally has exceeded 300,000, according to figures on the China Depository & Clearing Corp.'s Web site. So far this year, 20.9 million accounts have been opened, four times the amount in 2006, the clearing house's data shows.
The CSI 300 is now valued at 46 times earnings, making the mainland market the most expensive in the Asia-Pacific region.
Greenspan last week joined central bank Governor Zhaou Xiaochuan and Asia's richest man Li Ka-shing in warning of a bubble on China's stock market. The index fell 0.5 percent the day after Greenspan's comment. It resumed its gains the next day, closing 1.7 percent higher.
The CSI 300 has climbed 15 percent since May 6, when the central bank's Zhou said he was concerned about stock valuations. It also rose to a record after billionaire Li on May 17 said the market ``must be a bubble.'