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Infrared Difference Dust Index (IDDI) is often used as a satellite dust product to detect the change of mineral dust aerosols in the atmosphere. And aerosol optical depth (AOD) is also a main measurement for mineral dust aerosol. To qualify dust loading on the regional or global scale, it is very necessary to understand the relation between IDDI and AOD. Therefore, this study investigates the impact of sensitivity factors including surface temperature and surface type to the IDDI by using MODTRAN (Moderate Resolution Transmittance code) model to better evaluate the relation between IDDI and AOD. The result shows that the simulated IDDI from MODTRAN are extremely sensitive to the surface temperature and surface type. The IDDI is growing with the increased surface temperature. And the sensitivity of farm and forest type to IDDI is similar and their difference is very small. But the sensitivity of desert type and ocean to IDDI is obviously different from other two types and the surface type is also a key parameter to IDDI. The result also implies that there is an exponential relationship between IDDI and AOD. These results will be very helpful to further establish the relation between IDDI and AOD.