Existence. Risk-free arbitrage is to use the inefficiency of the market to obtain risk-free income. That is to say, the market does not price assets, so you can buy cheap assets and sell expensive assets. For example, in spot and futures markets, futures value is the future value of spot value. For example, if the spot price is 10 yuan and the one-year risk-free interest rate (such as bank deposit) is 10%, then the value of one-year futures should be 1 1 yuan. If the futures are 12 yuan at this time, it means that there are arbitrage opportunities, then short the futures and buy the spot. Finally, the spot price of futures will converge, so that risk-free income will be obtained at the final delivery.

But if there is such an opportunity, someone will arbitrage immediately and the market will take effect immediately, so it will appear in a short time. At the same time, there is also the risk of default at the time of final delivery. Moreover, in reality, the cost of arbitrage trading needs to be considered, and it makes sense that the cost is lower than the profit of arbitrage. But also need to have a more correct pricing for each asset. Generally, computer trading is used to arbitrage. It is still difficult for individual investors to obtain risk-free arbitrage.