There is evidence showing a long-term weakened trend of the tropical Pacific Walker Circulation under global warming condition, consistent with the expectation that the circulation will be weakened further. But recent research shows that the Walker Circulation has intensified over the recent decades. Is there any contradiction between the two? We analyzed the strength change of the Walker Circulation during the last decades using the reanalysis data of the tropical Pacific over the 36-year period from 1979 to 2014. The result showed an overall trend towards a stronger La Nina-like Walker Circulation. On the interannual timescale, the El Nino-Southern Oscillation (ENSO) accounts for much of the variability in the Pacific Walker Circulation; but the strengthening of the Pacific Walker Circulation in the recent decades cannot be explained by global warming or ENSO. The Indo-West Pacific sea surface temperature (SST), the Indian Ocean-Pacific Walker Circulation, the SST over the Indo-Pacific region, and Maritime Continent area's upward movement constituted a simple positive feedback system: stronger Walker Circulation accelerates more warm water to the warm pool area. Warmer SST in the warm pool region strengthens the convergence and upward motion over the Maritime Continent, which makes the Walker Circulation stronger. Besides, the Pacific Decadal Oscillation (PDO) was in the transition from cold phase to warm phase over the past decades, which intensified Pacific zonal SST gradient. The tropical Indo-West Pacific warming, tropical central eastern Pacific cooling and a closer connection between the two basins were the reasons of enhancement of Pacific Walker Circulation over the past decades.