With the continuous deepening of the spot market construction, the problem of unbalanced funds has become the key resistance to the regular operation of the spot market. Unbalanced funds are closely related to the characteristics of the market. Based on unilateral market mode and from the point of view of reducing the scale of dual-track unbalanced funds, a base for bottom settlement mechanism is designed. A settlement model of volatility unbalanced funds and congestion unbalanced funds under the base-forbottom settlement mechanism is proposed, and the correctness of the model by an example are put forward. The impact of the base for bottom settlement mechanism on volatility unbalanced funds and the interests of market players are analyzed, as well as the impact of contract signing of market entities on congestion unbalanced funds. In order to reduce the impact of unbalanced funds on the spot market and ensure a smooth start of the spot market, some suggestions are put forward from the aspects of market opening rhythm and market settlement mechanism.