Abstract: To analyze the process of hand-timing and the resulting data collected from the hand-timing computer system(HTCS)，in-cluding the timing operator′s reaction times of starting and stopping the watch，the results from the timing，the simulated electronic timing，the major factor that affects the time-keeper′s accuracy of time-keepingwere studied，i.e.the stability of the time-keeper′s reaction time，rath-er than the time-keeper′s reation time.The leading cause that inflicts error between the hand-time-keeping and the electrionic time-keep-ing consists in the pitfall that the time-keeper makes a wrong judgment in stopping the watch.The analytical results provide theoretic gist for the selection and training of time-keeping operators.

    Key Words: Hand-timing;Simulated electronic timing;Dynamic-timing;

     1 INTRODUCTION

    Hand-timing is widely used in track and field sports meet and swimming sports meet，because its cost is quite low and it′s simple and secure for the time-keepers to operate it.With the rapid development of science and technology，dynamic-timing system did appear.The re-liability of timing has been increased(precision of Dynam-ic-timing has reached10-3second.)[1] ......