The incineration technology of oil-based cuttings has been widely used. However, the environmental risks and main formation mechanism of oil-based rock cuttings incineration tailings have not been widely concerned.Through actual sample collection and laboratory simulation, combined with a variety of characterization methods, this study conducted a study on the conversion of barium and the environmental risk characteristics of incineration tailings in the typical rotary kiln incineration disposal process of oil-based rock cuttings from natural gas exploitation in Sichuan Province.The research results showed that the barium leaching toxicity level in the incineration tailings of oil-based cuttings was incinerated increases significantly. The main reason for this phenomenon was proved that barium sulfate in oil-based cuttings was transformed to barium sulfide by carbothermic reduction reaction above 800℃, and reacted with hydrogen chloride to produce barium chloride. This reduction conversion process mainly occured on the surface of barium sulfate crystal particles, and these barium sulfate crystal particles wrapped by soluble barium shells were finally formed. Carbothermic reduction conversion of barium sulfate may occur in reductive high-temperature heat treatment processes such as oil-based cuttings incineration, co-processing of oil-based cuttings in coal-fired boiler, and water-based cuttings and oil-based cuttings deoiled dry residue making sintered bricks. The conversion of barium during heat treatment and the environmental risk of high-soluble barium in solid phase should be widely concerned and effectively prevented. The control over this problem from the aspects of standard policy formulation, risk source prevention and control, and tailings terminal treatment were recommended in this paper.