A Non-invasive hyperthermia ablation technique of adipose tissue using a microwave is proposed. It uses dielectric heating to heat the adipose tissue using a rectangular Horn antenna. A selection of operating frequency 5.8 GHz, as an industrial, scientific, and medical radio bands (ISM band), for concentrating electromagnetic (EM) power radiated from the external antenna to the adipose tissue. To protect skin from heat, a silicon layer is used on the surface of the skin instead of water bolus to reduce the percentage of burns on the skin surface. The performance of this antenna is applied in three biological tissues (skin, fat, and muscles), using the simulation of computer simulation technology (CST) microwave studio. The main feature in this antenna is the centralization of the Specific absorption rate (SAR) at the fat tissue more than other tissues. Finally, results achieved good matching of the return loss (S11), and linear SAR value became high at fat tissue more than other tissues, and also the temperature distribution inside fat tissues became 42.7 °C while keeping the temperature inside the skin and muscles below 40 °C after 30 minutes.