Abstract: The history of mechanical extensometers including Huggenberger extensometer, Marten extensometer, Baoyashinnov extensometer and spherical joint extensometer was reviewed. In order to deduct the bending deformation of eccentric tension from the tension test results, two extensometers were required at each side of the tensile specimen to measure simultaneously during the tensile process. The modern electronic extensometers including one-side electronic extensometer, average value extensometer, two-side electronic extensometer, video extensometer and automatic extensometer were also introduced separately. The author expressed a different view on the unilateral measurement method of electronic extensometer, and the author thought the extensometers would be more automated, digital and remote sensing in the furture.