Seasonal drought is a main disaster for agricultural production in Guanzhong Plain, and research on spatial distribution characteristics and variation patterns of droughts under the global climate change is of great theoretic significance and applied value. Based on time series of drought monitoring results of vegetation temperature condition index (VTCI) from early March to late May during 2003 to 2014, the structural similarity (SSIM) was applied to analyze spatial characteristics of the time series of VTCI in the plain, and impact factors which affecting the spatial characteristics were analyzed as well. The results showed that the spatial characteristics of VTCI in Guanzhong Plain had distinctive regional variations and spatial heterogeneity, and the structural factor was the main factor affecting the variations. In general, the spatial variations of VTCI were influenced by the distribution pattern of water and heat conditions and terrain, as well as the microtopography, the underlying surface and the human factor. The variations were highly correlated and very sensitive to the changes in the microtopography, the underlying surface or the human factor when they became the dominant factors. Compared with other analytical methods that used some indexes as the indicators of droughts or made statistical models, the SSIM which has the structure information of images was a better approach for indicating the spatial characteristics of the droughts and their variations quantitatively, accurately and conveniently.