Abstract: A compression spring was tested in various compression speeds according to GB/T 1239. 2:2009 and the force-deformation curves were gained. The curves were processed by linear regression method and chord method respectively to calculate the spring stiffness. The uncertainties of the results were evaluated and compared according to JJF 1059. 1:2012. The results show that the expanded uncertainty of stiffness measurement of compression spring was 0. 82 N·mm^-1, which was mainly determined by the force value of testing machine and deformation measurement error, and it was less affected by the compression speed and data processing method. When the speed was low and processed with linear regression, the uncertainty caused by the repeatability of measurement could be reduced, but there was almost no difference in the expanded uncertainty of final measurement under different methods.