Abstract: Aiming at the problem that the representativeness of primary coal sampling cannot be quantitatively analyzed, discrete element simulation is introduced to analyze the primary sampling process in the middle of the belt and develop particle backtracking technology. At the same time, referring to the principle of judging representativeness of sampling in GB/T 19494-2004 "Mechanized Coal Sampling", using statistical parameters such as dispersion coefficient and position standard deviation after particle backtracking to analyze the backtracking particles, the quantitative research method of the primary sampling’s representativeness in the middle of the coal belt is established. Taking the primary sampler on a 2m wide coal conveying belt with a belt speed of 5m/s as an example, the sampling representative of the sampler at different speeds is quantitatively analyzed. The conclusion shows that the cutting speed of the cutting bucket ranges from 6.03m/s to 6.03m/s. When changing between 9.05m/s, the dispersion coefficient remains between 0.5321 and 0.5249, that is, the cutting speed has no significant influence on the representativeness of its sampling. The position standard deviation along the coal flow direction decreases faster with the increase of the cutting speed. The drop from 0.3326m to 0.2157m means that as the cutting speed increases, the distribution of collected particles becomes more concentrated.