The change of foreign exchange reserves is affected by many factors such as foreign investment and trade, foreign exchange system, foreign exchange rate fluctuation and capital outflow and so on. The analysis and prediction based on the macro-data during 2005—2018 show that the influence of China’s foreign investment and trade has regional difference, the investment and net export to “the Belt and Road” regions can reduce foreign exchange reserves, however, the investment in non-“the Belt and Road” regions has no significant influence on China’s foreign exchange reserves, the net-export to non-“the Belt and Road” regions can increase foreign exchange reserves. “Letting private agency hold more foreign exchange" can decrease foreign exchange reserves, the direction of the fluctuation of RMB exchange rate is not consistent in short-term and middle and long-term, the depreciation of RMB to US dollars will reduce foreign exchange reserves in short-term but will increase foreign exchange reserves in long-term. In above factors, the role to “let private agency hold more foreign exchange" is the biggest, the role of foreign trade is stronger than foreign investment, and the role of investment trade for “the Belt and Road” regions is far bigger than that of non-“the Belt and Road” regions. In several years, China’s foreign exchange reserves will tend to decline. As a whole, “the Belt and Road” construction has certain impact on the recently declining of China’s foreign exchange reserves, the influencing degree is not so big as some researches estimate and predict, but it will probably bring continuously consuming pressure on China’s foreign exchange reserves. Therefore, the judgment on the trend of China’s foreign exchange reserves change needs to specifically focus on “the Belt and Road” construction, China-US economic and trade friction, RMB exchange rate and so on and further to estimate and optimize the quantity and structure of foreign exchange reserves. China should strengthen classified management on foreign exchange, scientifically review the using performance of foreign exchange for “the Belt and Road” construction, and actively boost RMB internalization to reduce the consumption of foreign exchange in foreign economic and trade activities.