The emissions of heavy metals during coal utilization exert severe adverse impacts on the public health and ecosystems, which has attracted widespread attention throughout the world. The determination of the chemical forms plays a key role in the study of the heavy-metal partitioning behavior. However, due to the complex nature of coal, researchers haven't reached a unanimous agreement on the modes of occurrence, association, distribution, and concentration information of these elements. In this paper, a direct, non-destructive, and single-particle analytical method, i.e., synchrotron radiation-induced X-ray fluorescence spectrometry (SR-XRF), was utilized to study the micro-scale characteristics of heavy metals in coal. The forms of occurrence, spatial distribution, and associations of several concerned elements were visually inspected from mu-XRF maps. Besides, the size dependence characteristics of elemental composition, spatial distribution, and speciation in raw coal particles were featured. Finally, the detected elements were categorized into three groups according to their different affinities and size-segregated behavior. The size effects on the distribution patterns of the elements in coal particles were summarized. (C) 2016 Elsevier Ltd. All rights reserved.