In order to gain understanding of how model configurations affect simulated MJOs, we have conducted systematic sensitivity tests using the two established MJO events simulations. A reference simulation is carried out using ultra-high resolution (~250m horizontal and vertical), large-domain (~1000 km) and three-dimensional configuration. Comparisons between the reference simulations and field campaign observations show good agreements. Sensitivity tests with the same GCE model are then compared with the reference simulations in order to understand how these factors affect MJO simulations. The sensitivity factors include two-dimensional vs. three-dimensional simulations, changes of domain size and model resolutions, as well as different microphysical schemes. These sensitivity tests are compared with the reference simulation to understand how domain size, resolution and microphysics affect simulated MJO events. Our emphases are on how these factors affect surface rainfall pattern, cloud top height distributions, the vertical velocities, as well as simulated diurnal variations during DYNAMO field campaign.