The behaviour and performance of coke in a blast furnace is based on a complex system of chemical attack (reaction with CO2), thermal stress (temperatures up to 2300 °C) and mechanical strain (load processes and strain of the batch). For a better understanding of the parameters that are affecting coke properties, investigations were done on different, industrial produced and processed coke samples as well as on one sample taken from the tuyeres of the blast furnace. An established method for characterizing the effect of chemical attack, the Coke Reactivity Index (CRI), according to ISO 18894, was applied and represents the basis of the experimental work. Furthermore, the modification of the test parameters is a major part of this thesis. The strength of the coke during the process plays an important role and is measured with the Coke Strength after Reaction index (CSR). This value is closely related to the CRI. The influence of the chemical analyses and the accompanying elements of the coke samples (alkalis have a big influence) are also investigated. Additionally the specific surface area of the samples was measured and correlated to the CRI by means of the B.E.T.-method. Within this research work, the correlation of reactivity and strength as well as the dependence of these parameters on the chemical analysis, specific surface area and size fraction of the coke samples could be pointed out.