The mean stress correction model of random-amplitude fatigue stress spectrum and cumulative damage model for HRB500 reinforcing bar used in longitudinally connected ballastless track on bridge in service life under combined loads were studied to provide the support for the establishment of fatigue life prediction model for above mentioned HRB500 reinforcing bar.Through the constant-amplitude fatigue tests on standard specimens of HRB500 reinforcing bar，the influence law of mean stress on fatigue life of HRB500 reinforcing bar was studied，and the applicability of mean stress correction models of random-amplitude fatigue stress spectrum commonly used in practical engineering to HRB500 reinforcing bar was studied.Through the three-level variable-amplitude fatigue tests on standard specimens of HRB500 reinforcing bar，the applicability of Miner’s rule to the calculation of cumulative damage of the HRB500 reinforcing bar was analyzed.The research results show that the fatigue life of standard specimens of HRB500 reinforcing bar decreases with the increase of mean stress，Goodman model widely used in practical engineering is applicable to the mean stress correction of HRB500 reinforcing bar under random-amplitude loading，and Miner’s rule is suitable to calculate the cumulative damage of HRB500 reinforcing bar used in longitudinally connected ballastless track on bridge in service life under combined loads.