A new in-situ electrochemical scanning tunneling microscope (ECSTM) has been designed in our laboratory with the following main features: (1) The normal electrochemical current at the tip during scanning can be automatically corrected by a newly designed special feedback loop and computer program. (2) The tip-sample bias potential and the individual electrode potential of tip or sample can be adjusted, scanned or cycled by computer according to the requirement. (3) Driving and adjusting the tip to a nanometer distance from the sample surface can be carried out by a computer-controlled motor. A preliminary example of application to electrochemical systems is presented.