Under the dimension of US constitutionalism, freedom of speech is imprescriptible, while limitation to obscene speech in judicial practice becomes exception of the stipulation of US Constitution “prohibiting laying down the law”. Furthermore, coordination of conflicts between the two turns to be the target sought by the Federal Supreme Judicial Court. Prejudication on games between the two by the Supreme Court approximately went through three periods, namely, “Hicklin Norm” period, “Roth Norm” period and “Miller Norm” period, transiting from the standards of “those who are most likely to be influenced”, and “sort of obscenity”, to standards of “normal people” and “totally not redeeming social value”, and then to the standard of “serious value”. The Supreme Court attempted to seek for a balance between implementation of freedom of speech guaranteed by the Constitution and obscene speech.