Objectives To study the Electrophysiologic characteristics and method of radiofrequency ablation in patients with slow conduction in left free wall. Methods When 5 cases induced tachycardia, using VS2 program stimulation terminated the tachycardia to establish that ventricle is the part of reentry circle. Results No retrograde A waves in 4 cases but only 1 case present A wave in terminating tachycardia. The accessory pathways have decreasing conduction in One case. Successful ablation were located in ventricle sides. Conclusions Ventricular sense and S2 program stimulation to terminate tachycardia is a reliable method to different atrial tachycardia. A wave of successful targets ahead of A wave of any coronary sinus leads is 8 ～22 ms.