The mainland's benchmark Shanghai Composite was 1.3% down to 3,751.48 points.
The negative open comes after the index had seen strong volatility since the beginning of the week.
Traders appeared not to pick up on efforts by the central bank to provide more liquidity to stabilise markets.
In Hong Kong, the Hang Seng index was also pulled lower, down 1.1% to 22,905.80 points.
Shares across the rest of Asia also fell on Thursday over worries about China's slowing growth and volatile equities.
The region's largest stock market, Japan's Nikkei 225 index was down 0.4% at 20,142.81 points.
On Wednesday, China's Shanghai Composite fell by 5% at first before recovering to close 1.2% higher.
Sentiment was also muted by the weak lead from Wall Street overnight where oil companies saw sharp declines after another drop in the price of crude.
The minutes from the July meeting of the US central bank, the Federal Reserve, also failed to inspire markets.
The minutes showed policymakers thought conditions for a US rate rise "were approaching", but there remained worries over inflation and the strength of the global economy.
In Australia, the S&P/ASX 200 index dropped 1.1% to 5,318.80.
But there was better news for the country's national carrier, Qantas, which reported a return to full-year profit. Shares in the airline edged up by 0.7%.
In South Korea, the benchmark Kospi index fell 0.5% to 1,930.61 points.
After days of volatility Chinese equities traded lower once again on Thursday, despite Beijing's efforts to calm markets.