China's stock index futures closed mixed Wednesday with the contract for August, the most actively traded, down 0.35percent from the previous trading day to end at 2,873.8 points.

The September contract dipped 0.1 percent to 2,889.2 points. The December contract was up 0.01 percent to 2,931 points, and the March 2011 contract increased 0.16 percent to 2,971.2 points.

The stock-index contracts, agreements to buy or sell the Hushen 300 Index at a preset value on an agreed date are designed to allow investors to bet on and profit from both gains and declines in the market.

The index futures was launched at the China Financial Futures Exchange (CFFEX) and started trading from April 16, 2010. The CFFEX has set the base value for all the four contracts at 3,399 points.