Available funds are the funds that investors can deposit in stock index futures accounts to withdraw cash and open new positions. According to the debt-free settlement system of the day and the control degree of the intra-day trial settlement wind, after the settlement, investors will change the available funds in their accounts due to the changes of floating profit and loss of positions, closing profit and loss, transaction costs and position margin. When the available funds are negative, investors should take corresponding measures in time to prevent the risk of forced liquidation.