Radiofrequency ablation technique is one of the tumor hyperthermia methods and has been widely used in clinical treatment because of its small traumatic, better curative effect and others advantages. Recently, the common automatic control of radiofrequency ablation system is temperature control model that only used to control electrode tip temperature by controlling center of the output power to prevent cooking, rather than monitoring temperature of tumor edge, leading to the result is not accurate. So for the purpose of being ablated completely without damaging the normal tissue, this paper puts forward with double temperature controlling system to monitor the electrode tip and the tumor edge temperature at the same time, and control the output power according to the change of the temperature, in order to achieve the purpose of accurate ablation. Now The design of radiofrequency ablation signal have been finished, including the final output signal peak-to-peak voltage of 140V, current 0.3A, total power adjusted in 2W to 18W.