Lead exposure has long been recognised as a threat to human health. In the last century, tons of studies demonstrated the adverse health effects of lead exposure on neural and haematological systems in human body, and resulted in the restrain of lead use, including the elimination of leaded gasoline and lead-containing paint in the past decades. This study was aimed to profile preschool children blood lead level distribution around the world. Information on blood lead levels was obtained based on peer reviewed articles accessed through dataset like PubMed, etc. Study subject inclusion criteria were set as children aged 1–7 years old without hot-spot lead exposure. Collected data were plotted in chronicle by group of UN Human Development Index (HDI) to establish the transition trends of blood lead levels in the past three decades. For the very high HDI countries, the mode of blood lead level of preschool children was reduced from 4~6 µg/dL to 0.8~1.5 µg/dL, while that for the high HDI countries was down from 8~12 µg/dL to 3~5 µg/dL, and no substantially decrease was observed for the medium and low HDI countries. Extrapolation analysis showed the decreasing trend would reach the possible ground level of around 0.3~0.5 ug/dL for the very high HDI countries in the next two decades. Results of this study provided advices on strategy planning and source allocation for lead exposure prevention across countries of various extent of development.