The major drawback of microwave drying is non-uniform heating which may result in low quality dried products. To monitor the electromagnetic field distribution, a simulation process using Finite Element Methods was conducted. Three geometries in different sizes were selected as the microwave cavity. Analysis of variance for the non-uniform heating index showed that cavity size has significant effect ( p < 0.05) on the index. Additionally, it was shown that in cube and cylinder type cavities, the positioning of the lamp has no significant effect on the electromagnetic field distribution. However, this is not true when more than 1 lamp is used. Experimental validation of simulated results proved that simulation can cover the pattern of temperature distribution with R² of 0.96.