A new way of utilizing oil shale is its co-retorting with wheat straw for oil. However, the process generates a great amount of combustible solid semicoke waste. To utilize this waste effectively for heating the retorting process, the current work investigated its oxidation characteristics by employing a combined thermogravimetry-mass spectrometry (TG-MS) system, and discussed the effects of three parameters, including the wheat straw mass fraction of matrix samples, as well as different ambient gases and their O-2 volume fraction, on the oxidation of the semicoke. In the presence of O-2, the whole oxidation process of semicoke samples mainly consists of two stages: the combustion stage (300-600 degrees C) in which water, CO, CO2 and pollutants are mainly released, and the decomposition stage (600-1000 degrees C) in which carbonates and sulphates decompose to release CO2 and SO2, respectively. In the combustion stage, increasing both the wheat straw proportion of the original sample and the O-2 volume faction can improve the combustion performance of the resulting semicoke blends. In the decomposition stage, the gasification reaction also occurs to produce CO. During the entire oxidation process, semicoke in 21% 0 2 /79% CO2 would give off less NOx and SO2 than in air. And, SO2 formation is also influenced by the O-2 fraction, especially above 900 degrees C.