Atwistedfiberopticsensorbasedonintensitymodulationisdescribed.Theprincipleandstructureofthesensorandthechoiceofsteelstrandmodulesareintroduced.Thesensorisusedtodeterminethetensilestrainanddistribution.Theexperimentalresultsshowthatthechangeofthetransferringlightpowerhasanapproximatelinearrelationwiththeouterforce.Theintelligentsteelstrandswiththiskindofsensorwillhaveagoodapplicationinmonitoringtheconcretecrackanddeformationdistributioninhugestructuressuchasdamsandbridges.