The assessment of GHG emissions from spring wheat cropping system in Saskatchewan was conducted in this study. A general emission assessment model was developed. The main sources of GHG included emissions from farming operations, emissions from the manufacturing and transportation of N/P fertilizer, emissions from herbicides usage, and direct and indirect emissions from agricultural land. A case study based on spring wheat in Saskatchewan was then investigated. The results show that the total GHG emissions mainly come from the manufacture, storage, delivery, and application of nitrogen and environmental conditions have a significant effect on the total GHG emissions. In addition, a factorial analysis has been applied to evaluate the impact of uncertain parameters on system performance. In the case study of spring wheat crop in Saskatchewan, the total GHG emission is around 3,358,451 Mg CO2-eq. The results indicate that GHG emission is affected by environmental condition. From north to south Saskatchewan, the total GHG emission is decreasing as humidity decreased. The total GHG emission is mainly related to N fertilizer application, which accounts for about 80% of total emission. Through applying multivariate factorial analysis, the effects of uncertain parameters were identified, and the main effects and their interactions were also examined. The results have important implications for our efforts to evaluate the GHG emission from agricultural activities.