Inthispaper,thebackwardproblemoraparabolicequationisconsidered.Threenewstabilityestimatesaregiven.Basedonthenewstabilityestimates,aregularizationmethodisproposedforwhicherrorestimatesareavailable.Theregularizationmethodcanbeusedforthenumericalapproximationsoftheoriginalproblemwhichwillbeshownbythenumericalexamples.