Using a newly-developed population mixing technique we have studied the exciton dynamics in self-organized InAs/GaAs quantum dots (QDs).It is found that the exciton lifetime in self-organized InAs/GaAs QDs is around 1ns, almost independent of InAs layer thickness.The temperature dependence of the exciton lifetime varies from sample to sample,but no obvious experimental evidence was found that the lifetime is related to the δ-function of density of states in QDs.We have also found that the population mixing technique can be used to directly reveal the band-filling effect in the excited states of the QDs.