Objective To study the relationship between on-line correction and stiffness of the upper limb during human movements, so as to improve the measurement accuracy of stiffness and to assess the on-line correction capability. Methods Five kinds of upper limb goal-directed movements in a horizontal plane were designed. The stiffness values at 5 different positions, i.e. in the early period, early to mid period, mid period, mid to late period and late period separately during the movements with sudden perturbation were measured to investigate the regular pattern of human hand stiffness influenced by such on-line correction, as well as the relationship between the movement accuracy and hand stiffness. Results The stiffness was always varying during the movements, and the variation of the stiffness would influence the movement error. On-line correction during the movements could induce an increase in the value of stiffness amplitude, especially at the position in late period of the movement. However, no significant linkage was found between the change of stiffness and the occurrence time or content of on-line correction. Conclusions On-line correction plays an important role in goal-directed movements. Considering that on-line correction may cause a change in the amplitude of the stiffness, the on-line correction function of patients can be more accurately assessed by measuring stiffness value in specific experiments, combined with other medical diagnosis methods in clinic.