Given the scale of the Chinese economy, the 7.4 growth in 2014 is very high compared with other major economies, and China is still a "key engine" of global growth, contributing the most to global economic expansion in the past year, said Milesi-Ferretti, who oversees the WEO update.

With the Chinese economy moving in the "new normal" period, Chinese policymakers are calm facing the slight slowdown of economic growth, because China is set to transition to an economy more reliant on consumption instead of investments with more stress to be laid on quality of the growth, Milesi-Ferretti said.

China is confronted with some domestic vulnerabilities including the real estate sector, waning export demand and geopolitical risks, but the decline of the oil price will help enterprises lower operational costs. Economic restructuring in the long run is good not only for China but also the rest of the world, he added.

The IMF predicted the Japanese economy would edge up 0.6 percent and 0.8 percent in 2015 and 2016, down 0.2 percentage point and 0.1 percentage point from its previous projections.

It forecast the Russian economy to contract by 3 percent and 1 percent in 2015 and 2016, down 3.5 percentage points and 2.5 percentage points from its previous projections.