Abstract: Various kinds of non-classical logic sprang up vigorously while classical logic came to a standstill relatively in the 1960's.After reflecting on many inconsistent propositions in the fields of logic,natural science and social science people began challenging classical logic and believed that the law of contradiction was not valid universally.In the background da Costa founded paraconsistent logic.When appling paraconsistent logic to alethic modal logic,we get a deontic logic system which avoids the Good Samaritan Paradox.Therefore we can conclude that deontic logic can be reduced to paraconsistent alethic modal logic.