Regional Comprehensive Economic Partnership (RCEP), officially entered into force on January 1st, 2022. It remains to be seen whether India’s withdrawal from RCEP is permanent, but if it returns after the effects of RCEP have gradually become evident, the basis for calculating its domestic trade gains and losses as well as the implications for member countries at the macroeconomic level is undoubtedly a matter of concern. This paper uses the GTAP model to simulate India’s trade gains and losses under different scenarios whether it joins or does not join RCEP. The results show that the level of total national welfare and total output of each member country will be higher after the RCEP agreement enters into force, regardless of India’s membership. But India’s withdrawal from the RCEP will have a negative impact on the growth of its total exports and imports. If India returns to RCEP, it will not only have a positive pulling impact on the growth of its own export and import trade, but will also have a greater trade growth effect on the other members of the agreement. In addition, India's accession to the RCEP does also carry a certain degree of risk of increasing the external trade deficit. In this regard, looking forward to the prospect of India’s accession to the RCEP, the following predictions and insights can be drawn: India may choose to rejoin the RCEP agreement at the appropriate time course rather than withdrawing permanently; India’s return to RCEP could bring new impetus to China’s economic development; China should actively use diplomatic and economic sources to urge India to return to the RCEP agreement as soon as possible, so as to create better conditions for economic growth for both China and India in the future.