Abstract: The laser flash method is widely applied in the field of thermal management and insulation materials due to its advantages of small sample, rapid testing, high precision, and broad applicability. However, thermal conductivity (κ) is an indirectly calculated value, and its accuracy is limited by the measurement errors of three parameters: thermal diffusivity, specific heat capacity, and density. Among these, the influence of sample state and testing conditions on thermal diffusivity is particularly significant. This paper systematically investigates the effects of sample dimensions, detection area, and correction models on thermal diffusivity measurement. Concurrently, specific heat capacity was precisely measured using Differential Scanning Calorimetry (DSC), and the linear expansion coefficient (used for density correction) was determined using Static Thermomechanical Analysis (TMA). These data were integrated into the analysis software to calculate thermal conductivity. Comparative analysis reveals that the differences in thermal conductivity values obtained by different calculation methods primarily stem from errors in specific heat capacity measurement.