Microwave ablation is a treatment method that effects malignant tissue area directly without damaging surrounding healthy area. Microwave energy lead to rise tissue temperature instantly and coagıulation occurs. Micro coaxial slot antennas ere employed to apply ablation process. The main objective of this work determine the efficiency of antenna geometry on the ablation process. Three different slot coaxial antenna models (single slot, double slot and sleeved) are employed to comparison and exposed to power of 10w, 20w and 30w during 10 minute. The COMSOL MULTIPHYSICS (ver 4.3, COMSOL Group) software is employed to design and simulate antennas. Eventually ablation length, ablation diameter, temperature, special absorption rate and power dissipation are obtained with finite element method from the electromagnetic simulations using COMSOL. Experimental validations were designed to evaluate the proposed antenna. Model verification and simulation results have been evaluated in effective antenna geometry.