The invention discloses an electrochemical sample fixture and an electrochemical in-situ experimental device in a scanning electron microscope. The fixture comprises: two aluminum matrices and two polymer coatings; a first through hole and a second through hole are formed in the first aluminum matrix; a thermocouple and a temperature adjusting device are bonded by ceramic glue, are placed in the first through hole, and are buried by the ceramic glue; a first outgoing line is led out from the interior of the first aluminum matrix through the second through hole for connecting a temperature displayer at the outside of the scanning electron microscope; a second outgoing line is led out from the interior of the temperature adjusting device for connecting a control power supply; the two aluminum matrices have the same structure, and the two polymer coatings have the same structure; and the first aluminum matrix, the first polymer coating, the second polymer coating and the second aluminum matrix are assembled in sequence to form the fixture, and an electrochemical sample is placed between the first polymer coating and the second polymer coating. The electrochemical sample fixture disclosed by the invention is applicable to a variety of electrochemical systems, and meanwhile improves the range of electrochemical observation.