Issues of regional economic development inequality have been particularly important in China, which caught serious attention of economists and geographers. This paper takes capita GDP indications at city level to analyze spatial-temporal evolution of regional economic inequality in the Yellow River Valley during 1990-2013, by Theil decomposition, Exploratory Spatial Data Analysis(ESDA) and Spatial Markov chain, which can be realized by Excell, OpenGeoda and Pysal 2.7. It comes to the conclusion from two sides of time series and spatial series, as follows:Firstly, regional economic inequality of the Yellow River Valley is sensitive to geographical scale, the inequality of the Yellow River Valley shows an inverted U shpe pattern. Secondly there exist obvious spatial heterogeneity and positive correlation in the Yellow River Valley. Thirdly, by using Spatial Markov chain method, we can analyze the characteristics of spatial and tempral evolution of the 73 cities in the Yellow River Valley in the past 24 years. Generally, if a region is adjacent to regions with low economic level, it will suffer from negative influences; if adjacent to regions with high economic level, it will help increase the number of regions with the economic level shifting upward and reduce the number of regions with same level or downward transfer.