A device for measuring thermal conductivity is designed and built by ourselves,which is attached to a Perkin-Elmer DSC-2C instrument.A method of determining thermal conductivity (λ) of small cylindrical samples and its expression for calculating λ is established. The thermal conductivities of 18 propellants,explosives and the related materials are determined. The results show that the deviation is ≤3.7%,lower than the internationally accepted limit of 5%.The values obtained from the present method are consistent well with those from the Guarded Hot Plate and Microcalorimeter. The experimental data of the reference materials are in agreement with their standard values.Meanwhile the influences of the dimension,the homogeneity and the end-faces parallelism of the sample on its thermal conductivity are discussed.