This research deals with the computational accuracy impact factors of elasto-plastic spectral element applications to slope stability. It contains three categories of impact factors: 1) modelling domain related parameters, 2) spectral parameters, and 3)X elasto-plastic parameters. Each category has many accuracy impact factors. The modelling domain and elasto-plastic related impact factors can be equally applied to the elasto-plastic finite element method, however spectral corrections can only be applied for spectral element applications. This work presents a numerical evaluation of all three impact factors to the stability factor of a slope in three representative theoretical domains of slope angle, of 26.26°, 36.69°, and 45°. In addition, the study focuses on spectral element applications to slope stability evaluation, because it is a new and reliable approach in slope stability modelling. It has several benefits over the existing modelling methods to apply for slope stability modelling: 1) geometric flexibility of the finite elements, 2) high computational efficiency, 3) reliable spectral accuracy, and 4) high numerical stability.