Theoretically, a currency with high interest rate will lead to the conversion of a currency with low interest rate into a currency with high interest rate for investment, which will lead to the inflow of foreign exchange. In fact, this situation generally does not happen, because short-term arbitrage will cause short-term RMB appreciation, but it will cause RMB depreciation when long-term arbitrage funds return. Long-term RMB depreciation is contrary to arbitrage gains, making arbitrageurs unprofitable. For example, the RMB interest rate is much higher than the US dollar interest rate now, but this has not happened because the exchange rate changes in arbitrage activities are in equilibrium. Another reason is that RMB is not a freely convertible currency, and the strict control under the capital account also inhibits arbitrage or increases the cost of arbitrage.