We have recently presented an extraction method, which we call degradative solvent extraction, for producing high quality extracts having similar physical and chemical properties from several types of low rank coals and biomasses. The degradative solvent extraction is an effective method to remove oxygen from low grade carbonaceous resources by dehydration and decarboxylation reactions, which minimize the loss of heating value of starting material. Three solid fractions, Residue, Deposit, and Soluble, were obtained from the extraction method when the product was fractionated. Soluble and Deposit are expected to be precursors for producing value-added products. Residue is expected to be utilized as a high quality solid fuel because of its high heating value comparable to subbituminous coal. When the extraction product was not fractionated, the product is the mixture of the three fractions just upgraded. We called the upgraded product "solvent-treated coal" (STC) when it was prepared from coal. STC is also expected to be a high quality solid fuel. To evaluate the potential of Residue and STC as high quality solid fuels, estimation of their propensity to spontaneous heating is essential in addition to their heating values and rates of combustion and/or gasification. In a previous work the authors have proposed that the weight change and the heat generation rate measured at 107 degrees C in both dry air and wet air can be an index to estimate the propensity to spontaneous heating. This work applied the method to estimate propensity to spontaneous heating of Residue and STC prepared from two low-rank coals. The propensity to spontaneous heating of the parent coals and chars prepared in an inert atmosphere at 350 degrees C is also examined for comparison purposes. It was found that the degree of propensity to spontaneous heating of Residue and STC is much less than that of the corresponding parent coal and chars.