Abstract: Abstract The maximum force total elongation of steel bars was measured using the extensometer method and manual method, and the causes of measurement errors in both methods were studied. An extensometer method was designed to measure and calculate the maximum force total elongation of steel specimens. The results were compared with the manual calculation results, and the reasons for the differences in the results obtained by the two calculation methods were analyzed. The influence of gauge length and steel bar specifications on the results of manually measuring the maximum force total elongation was studied. The gauge length had a greater impact on the measurement results, while the steel bar specifications had a smaller impact.