Food security is the basic foundation in accomplishing of the overall Sustainable Development Goals (SDGs). As the objective in SDGs of "halving the proportion of hungry people by 2015" has not been achieved as scheduled, it will become more challenging to realize its final goal of zero hunger by 2030. So exploring the underlying causes of global food security pattern from perspectives of spatio-temporal evolution is badly needed. In this paper, a comprehensive evaluation method with multi-indices was applied to evaluate the food security level of 172 countries in 2000-2014 based on an established global database with country-specific time series data. Then the spatial pattern and changing characteristics of global food security by country was conducted through the spatial autocorrelation analysis. Upon this basis, the underlying factors affecting the food security pattern were further identified and analyzed with a multiple nonlinear regression method. The findings and results show that: (1) The global food security pattern can be summarized as "high-high and low-low agglomerations" of socio-economic status and food security level. The most food secure countries are mainly distributed in the regions with more advanced economy such as North America, Oceania, parts of East Asia, and Western Europe. On the contrary, the least food secure countries are mainly distributed in sub-Saharan Africa, South Asia, West Asia, and parts of Southeast Asia. (2) At 99% confidence level, Western Europe and sub-Saharan Africa are respectively the hot and cold spots in global food security landscape, while in non-aggregation areas such as Haiti and North Korea, there exist long-term food insecurity problems. (3) The spatio-temporal pattern of global food security is generally stable, but the internal changes in the extremely insecure groups are significant. The countries with the most changeable levels of food security are also the countries with the most food insecurity. (4) Annual mean temperature, per capita GDP, the proportion of people who have access to clean water, and political stability are the key factors affecting the global food security pattern. The study indicates that while the global food security situation has improved since 2000, there was a reverse sign or omen in 2013. Affected by climate change, residents' purchasing power, infrastructure condition, and political and economic stability, global food security has in fact been volatile and some areas in the world are still facing acute food security problems. In addressing this challenge, a food security strategy based on the four dimensions, i.e. food supply, food access, food use and political stability, and a worldwide rural revitalization approach, is highly recommended. Meanwhile, it is necessary to progressively introduce some diversified modes of production such as urban agriculture to build a more resilient food system in those fully urbanized regions.