Abstract: As the world's second largest economy，the European Union has already experienced a short but fast growth in the middle and later period of 1990s，which affected its regional internal economic significantly. Illustrated by the 28 members of the European Union，this paper analyzed the evolution characteristics of regional economic disparity since the middle of 1990s by using the decomposition of Theil index，and explored the different spatial patterns of evolution by using inverse distance weighted interpolation method. The results were summarized as followed：（1）During the period from 1995 to 2015，the Theil index of the economic development presented an overall upward trend，which meant the regional disparities were being expanded. The regional differences of evolution can be divided into three stages：the slow-down stage of low difference from 1995 to 1999，the slow-down stage of high difference from 2000 to 2008，and balanced development stage from 2009 to 2015；（2）The between-groups Theil index of the economic development showed an overall stable fluctuated and declined slightly，but the extents and trends were varied in different periods. The evolution of the difference between groups can be divided into three stages：the expansion phase of regional differences from 1995 to 2000，the narrowing phase of regional differences from 2000 to 2009，and the expansion phase of regional differences from 2009 to 2015. The difference of regional economy tended to be a stable equilibrium state in the Northern Europe，while that of being gradually narrowed in differences in the Southern Europe region and the Central Europe. In the Eastern Europe，the economic differences between groups can be divided into four stages，which were expansion，steady，shrinking and smooth. And the economic differences between groups in the Western Europe can be divided into two stages: slow-down，balanced development；（3）The regional different pattern in the European Union is changing from polarized development to the balanced spatial pattern. And the change is not significant，presented an overall regional economic spatial pattern that gradually decreased with three circles：the Western Europe lies in the first circle，the Northern and Southern Europe are in the second circle，and the Eastern and Central Europe are in the third circle. This paper provides a theoretical supplement to the progress of regional economic differences in the European Union，and provides a practical guidance for the Chinese economic to enter the aforementioned economy development stages.