The phenomenon of wildland fires in the tropical area does not only occur on dry land, but also in wetlands such as peatlands, especially in the dry season which caused the wetlands to dry up then become more flammable. This peat fires are dominated by smoldering combustion that is the most persistent type of combustion. Previous researchers have studied about smoldering combustion behavior and gain some information that the combustion process on peatfires is a function of the moisture content, organic content and density of material, The literature review based on previous research was being an initial guidelines and observations were held by seeing the data that had been taken from laboratory-scale experiments of natural peat soil from Kampar, Indonesia with two types of inorganic modified content are 1:12 and 1:6. This experiment prove that modifying the inorganic content of a sample can affect the ability of peat to smoldering. From observations Natural Peat, Modified Peat 1 and Modified Peat 2 have the value of average smoldering spread rate ∼1.08 cm/h, ∼0.80 cm/h but the Modified Peat 2 was failed to smoldering because the heat generation was not enough to propagate the next deeper layer. The results of this research can provide new knowledge about effect of adding inorganic content and can be one of the basic references for further research related to the prevention of the widespread peatfires which is a serious problem for the environment.