Buying contracts in recent months and selling contracts in distant months are arbitrage, and the shrinking expansion is king. In futures arbitrage, when there is a shortage of supply, strong demand or relatively strong long-term supply in shopping malls, this situation is divided into bull spreads in the concepts and formulas of futures industry. Financial circles put forward a solution to this situation, that is, buying near and selling far is a cow's nest, and expanding while contracting is king. In the explanation, the explanation refers to buying the near-month contract, selling the far-month contract for arbitrage, and shrinking while expanding is the king, so the possibility of surplus is relatively large.