As the main advocate of investment liberalization, the United States has been spare no efforts in popularization of national treatment in the pre-establishment phase. However, the facts show that the United States lodge an elaborative reservation, when it devotes to high level investment liberalization rules, to step down the substantive treaty obligation of national treatment and put it under its control. In view of that the reservations in IIA are a key technique for preserving flexibility of national authorities, especially for developing countries. It is very important for China to introduce a systematical reservation rather than pursue the alleged “general national treatment standard” for foreign investment blindly.