The caking index of coal is one of the important indicators for evaluating plasticity of coal. In order to accurately measure the caking index of coal, the influence relations between various components of uncertainties and evaluation results of uncertainties for caking index of coal are analyzed in detail in the paper. The components of uncertainties include such influence factors as the standard uncertainty u(rep) introduced by repetitive tests, standard uncertainty u(m) introduced by weighing mass m of sample with the scale, standard uncertainty u(c) introduced by weighing coke residue during detection process of sample, standard uncertainty u(r) introduced by rotational speed of drum and standard uncertainty introduced by temperature changes of muffle furnace. The uncertainties of measurement results for the caking index of coal are obtained through calculating the standard uncertainties, which provide the basis for scientifically and accurately providing measurement results.