Abstract: The feed particle size requirement of Bond Standard Ball Mill Work Index determination is -3.2 mm，which is hard to obtain in some cases.Therefore，it is indispensable to study the relation between the Bond Standard Ball Mill Work Index and the material particle size.This is a significant theoretical guidance to broaden the application range of Bond Work Index，especially for the precision design and calculation of the second grinding mill and regrinding mill.Homogeneous material quartz and heterogeneous material iron ore as the experimental materials，and the Bond Work Index determination program was adopted to investigate the Bond Standard Ball Mill Work Index changing law with the feed particle size and the product particle size.Further，the mathematical model relationship was established between the Bond Work Index and the feed particle size as well as the product particle size.The test results indicated that with the controlled sieve size smaller，the Bond Ball Mill Work Index shows a trend of increase，and the increase of quartz is larger than that of iron ore.The relationship between the Bond Work Index and the control mesh size (μm) can be described by a quadratic function.The finer the feed size is，the coarser the product size（P₈₀） will be when the grinding cycle reaches equilibrium.However，when the mesh size is small to a certain extent，the granularity change of the product is not obvious.Whether it is homogenous material quartz or non-homogeneous material iron ore，the Bond Ball Mill Work Index changes exponentially with the feed particle size.The Bond Standard Ball Mill Work Index for homogenous material quartz ranges from 1.7 to 3.2 mm for feed size and 0.9 to 3.2 mm for heterogeneous material iron ore，the former is narrower and the latter is wider.If the range of the feed particle size is less than aforementioned，then the result of the measurement needs to be corrected.

Key words: Bond ball mill work index, Feed particle size, Product particle size, Control screen size, Function