The figure was down by nearly 40 percent from the volume in April, according to financial information service provider Wind.
Some 22 billion yuan worth of lock-up shares from 16 companies in the electronics industry will be eligible for trade this month, the data showed.
Under China's stock market rules, major shareholders must wait for one to two years before they are permitted to sell their shares.
Major Chinese stock indices ended higher on Thursday, the last trading day of April, with the benchmark Shanghai Composite Index up 1.33 percent to close at 2,860.08 points.
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